Information Disclosure Vulnerabilities

Information Disclosure Vulnerabilities refer to security weaknesses that allow unauthorized access to sensitive information. This information can be anything from personal data, confidential business information, to system configuration details. These vulnerabilities can occur due to various reasons, such as programming errors, system misconfigurations, and inadequate access controls.

There are several types of information disclosure vulnerabilities, including:

Directory traversal: This vulnerability allows an attacker to access files and directories that are outside the web root directory. It occurs when an application fails to properly sanitize user input and allows the attacker to navigate through the file system.
SQL injection: This vulnerability allows an attacker to execute SQL commands on a web application’s database. It occurs when the application fails to properly validate user input and allows an attacker to inject malicious SQL statements.
Cross-site scripting (XSS): This vulnerability allows an attacker to inject malicious scripts into a web page viewed by other users. It occurs when the application fails to properly validate user input and allows an attacker to inject code that is executed by other users.
Information leakage: This vulnerability occurs when an application unintentionally exposes sensitive information, such as passwords or database credentials, through error messages or debug information.
Insufficient authentication and authorization controls: This vulnerability occurs when an application fails to properly authenticate and authorize users, allowing unauthorized access to sensitive information.
Server misconfiguration: This vulnerability occurs when a server is not configured securely, such as leaving default credentials or configurations unchanged.

The dangers of leaking sensitive user or business data are fairly obvious, but disclosing technical information can sometimes be just as serious. Although some of this information will be of limited use, it can potentially be a starting point for exposing an additional attack surface, which may contain other interesting vulnerabilities. The knowledge that you are able to gather could even provide the missing piece of the puzzle when trying to construct complex, high-severity attacks.

Occasionally, sensitive information might be carelessly leaked to users who are simply browsing the website in a normal fashion. More commonly, however, an attacker needs to elicit the information disclosure by interacting with the website in unexpected or malicious ways. They will then carefully study the website’s responses to try and identify interesting behavior.

Some examples of Information Disclosure

Personal data disclosure: This occurs when an individual’s personal information, such as name, address, Social Security number, or credit card number, is released without their consent.
Intellectual property disclosure: This occurs when a company’s proprietary information, such as trade secrets, patents, or copyrights, is released without authorization.
System configuration disclosure: This occurs when system configuration information, such as usernames, passwords, or network topology, is released without authorization.
Revealing the names of hidden directories, their structure, and their contents via a robots.txt file or directory listing
Providing access to source code files via temporary backups
Explicitly mentioning database table or column names in error messages
Hard-coding API keys, IP addresses, database credentials, and so on in the source code
Hinting at the existence or absence of resources, usernames, and so on via subtle differences in application behavior

How do Information Disclosure Vulnerabilities arise?

Information disclosure vulnerabilities can arise due to various factors, including:

Improper input validation: One of the most common reasons for information disclosure vulnerabilities in websites is the lack of proper input validation. Websites that do not properly validate user inputs are susceptible to attacks such as SQL injection and cross-site scripting, which can result in the disclosure of sensitive information.
Misconfigured web servers: Misconfigured web servers can also lead to information disclosure vulnerabilities. For example, default directory listings or sensitive system files may be accessible to unauthorized users.
Insufficient access controls: Websites that do not have proper access controls can also be vulnerable to information disclosure. If access controls are not implemented properly, an attacker may be able to access sensitive information without proper authorization.
Insecure storage of sensitive data: Websites that store sensitive information such as passwords or credit card numbers without proper encryption or hashing can be vulnerable to information disclosure.
Vulnerable third-party libraries or components: Websites that use vulnerable third-party libraries or components may also be at risk of information disclosure if the vulnerabilities are exploited by attackers.
Human error: Human error, such as misconfiguring security settings or inadvertently making sensitive information publicly accessible, can also lead to information disclosure vulnerabilities.
Insecure configuration of the website and related technologies: For example, failing to disable debugging and diagnostic features can sometimes provide attackers with useful tools to help them obtain sensitive information. Default configurations can also leave websites vulnerable, for example, by displaying overly verbose error messages.
Flawed design and behavior of the application: For example, if a website returns distinct responses when different error states occur, this can also allow attackers to enumerate sensitive data, such as valid user credentials.
Failure to remove internal content from public content: For example, developer comments in markup are sometimes visible to users in the production environment.

Impact of Information Disclosure Vulnerabilities

Information disclosure vulnerabilities can have both a direct and indirect impact depending on the purpose of the website and, therefore, what information an attacker is able to obtain. In some cases, the act of disclosing sensitive information alone can have a high impact on the affected parties. For example, an online shop leaking its customers’ credit card details is likely to have severe consequences

On the other hand, leaking technical information, such as the directory structure or which third-party frameworks are being used, may have little to no direct impact. However, in the wrong hands, this could be the key information required to construct any number of other exploits. The severity in this case depends on what the attacker is able to do with this information.

Here are some examples of the impacts of information disclosure vulnerabilities:

Identity theft: If personal information, such as social security numbers or credit card information, is disclosed, it can lead to identity theft. Attackers can use this information to make fraudulent purchases, open new accounts in the victim’s name, or conduct other illegal activities.
Financial loss: If financial information, such as bank account or credit card information, is disclosed, it can result in financial loss for the affected individuals. Attackers can use this information to make unauthorized purchases or transfer funds.
Loss of trust: Information disclosure can result in a loss of trust between the website and its users. Users may be hesitant to share their personal or financial information with the website in the future.
Reputational damage: Information disclosure can damage the reputation of the website and the organization behind it. A data breach or other security incident can be newsworthy and result in negative publicity, which can affect the organization’s brand and customer loyalty.
Legal consequences: Depending on the nature and extent of the information disclosed, the website owner may be liable for legal consequences such as regulatory fines, lawsuits, or criminal charges.

How to find and exploit information disclosure vulnerabilities

Testing for information disclosure vulnerabilities

you should avoid focussing too narrowly on a particular vulnerability. Sensitive data can be leaked in all kinds of places, so it is important not to miss anything that could be useful later. You will often find sensitive data while testing for something else. A key skill is being able to recognize interesting information whenever and wherever you do come across it.

Here are some high-level techniques and tools that can be used to identify information disclosure vulnerabilities during testing:

Vulnerability scanners: Tools like Nessus, OpenVAS, and Qualys can scan a website for known vulnerabilities, including information disclosure vulnerabilities.
Web proxies: Proxies like Burp Suite and OWASP ZAP allow testers to intercept and modify web traffic, making it easier to identify and exploit information disclosure vulnerabilities.
Manual testing: Manual testing involves a tester manually interacting with a website to identify potential vulnerabilities. This can include trying to access restricted pages or directories, attempting to access data without proper authentication, and examining error messages for sensitive information.
Code review: A thorough review of the website’s source code can identify potential areas where sensitive information could be leaked or exposed, such as poorly secured API endpoints or unencrypted database connections.
Penetration testing: Penetration testing involves simulating an attack on a website to identify potential vulnerabilities, including information disclosure vulnerabilities. This can involve a combination of automated tools and manual testing techniques.
Static analysis: Static analysis involves analyzing the website’s source code or compiled binaries for potential vulnerabilities, including information disclosure vulnerabilities.

And there will be some details about fuzzing and engineering in the informative responses.

Fuzzing

is a technique used in software testing to identify vulnerabilities by providing unexpected or invalid input to a programme or system. The goal is to trigger unexpected behaviour and find vulnerabilities that may not be apparent through other testing methods. In fuzzing, a large number of random inputs are generated and fed into the system being tested, such as a website or application. These inputs can include invalid data, unexpected data types, or data that falls outside of the expected range of values. The system’s response to these inputs is then analysed for unexpected behaviour, crashes, or other anomalies.

For example, a web application may have a login page that accepts a username and password. A fuzzer might generate thousands of random usernames and passwords, including input that is outside of the expected range of values. The application’s response to these inputs would be monitored for any unexpected behavior, such as error messages that reveal sensitive information or unexpected behavior that could indicate a vulnerability.

You can automate much of this process using tools such as Burp Intruder. This provides several benefits. Most notably, you can:

Add payload positions to parameters and use pre-built wordlists of fuzz strings to test a high volume of different inputs in quick succession.
Easily identify differences in responses by comparing HTTP status codes, response times, lengths, and so on.
Use grep matching rules to quickly identify occurrences of keywords, such as error, invalid, SELECT, SQL, and so on.
Apply grep extraction rules to extract and compare the content of interesting items within responses.

Engineering informative responses

Verbose error messages can sometimes disclose interesting information while you go about your normal testing workflow. However, by studying the way error messages change according to your input, you can take this one step further. In some cases, you will be able to manipulate the website in order to extract arbitrary data via an error message.

There are numerous methods for doing this depending on the particular scenario you encounter. One common example is to make the application logic attempt an invalid action on a specific item of data. For example, submitting an invalid parameter value might lead to a stack trace or debug response that contains interesting details. You can sometimes cause error messages to disclose the value of your desired data in the response.

Common sources of information disclosure

Information disclosure can occur in a wide variety of contexts within a website. The following are some common examples of places where you can look to see if sensitive information is exposed.

Files for web crawlers

Web crawlers, also known as spiders or bots, are automated programs that browse the internet and collect information from websites. Web crawlers typically start with a list of URLs to visit, and then follow links on those pages to discover new URLs to visit.

Here are some files that are commonly used by web crawlers:

Robots.txt: The robots.txt file is a text file that is placed in the root directory of a website to provide instructions to web crawlers. The file can be used to specify which pages or directories should not be crawled, and can also be used to provide additional information a bout the website and how it should be crawled.
Sitemap.xml: The sitemap.xml file is an XML file that provides a list of URLs for a website, along with metadata about each URL. This file is used by search engines to discover and index content on the website.
RSS feeds: RSS (Really Simple Syndication) feeds are XML files that provide updates from a website. Web crawlers can use RSS feeds to discover new content on a website and keep track of updates.
JavaScript and CSS files: Web crawlers can also analyze JavaScript and CSS files to understand how a website is structured and how it should be crawled. This can be especially useful for websites that use dynamic content or single-page applications.
HTML files: Finally, web crawlers can analyze HTML files to collect information about a website, such as the title of each page, the content of each page, and any links or images on the page.

Directory listings

Directory listings are an index of the files and folders contained within a directory on a web server. When directory listings are enabled, anyone can view the contents of the directory by simply navigating to the directory in their web browser. Directory listings are typically used for websites that host public files, such as software downloads or publicly available documents. They can also be used to allow website administrators to easily manage and organize files on a web server.

However, directory listings can also pose a security risk if sensitive files or information are exposed. For example, if a directory listing includes files that should not be publicly accessible, such as configuration files or database backups, an attacker could potentially gain access to sensitive information.

Developer comments

During development, in-line HTML comments are sometimes added to the markup. These comments are typically stripped before changes are deployed to the production environment. However, comments can sometimes be forgotten, missed, or even left in deliberately because someone wasn’t fully aware of the security implications. Although these comments are not visible on the rendered page, they can easily be accessed

Occasionally, these comments contain information that is useful to an attacker. For example, they might hint at the existence of hidden directories or provide clues about the application logic.

Error messages

verbose error messages can definitely be a common cause of information disclosure and can provide valuable information to attackers during an audit. By providing detailed error messages, the website is inadvertently giving away information that could be used to exploit the system. verbose error messages can reveal information about what input or data type is expected from a given parameter, which can be used by attackers to identify exploitable parameters. Additionally, error messages can reveal the underlying technology stack of the website, including the software versions and components being used. This information can help attackers identify vulnerabilities and known exploits for the specific technologies in use.

Verbose error messages can also provide information about different technologies being used by the website. For example, they might explicitly name a template engine, database type, or server that the website is using, along with its version number. This information can be useful because you can easily search for any documented exploits that may exist for this version. Similarly, you can check whether there are any common configuration errors or dangerous default settings that you may be able to exploit. Some of these may be highlighted in the official documentation.

It’s important for developers to be aware of the information revealed in error messages and to ensure that error messages are appropriately sanitized to avoid exposing sensitive information. As part of a security audit, it’s also important to carefully examine error messages and to test whether the information revealed can be used to exploit the system. By identifying and addressing verbose error messages, developers can reduce the risk of information disclosure and improve the overall security of the system.

Differences between error messages can also reveal different application behavior that is occurring behind the scenes. Observing differences in error messages is a crucial aspect of many techniques, such as SQL injection, username enumeration, and so on.

For Practical Lab:

https://portswigger.net/web-security/information-disclosure/exploiting/lab-infoleak-in-error-messages

Debugging data

Debugging messages and logs can be a major source of information leakage and can provide attackers with valuable information about the application’s behavior and infrastructure. Developers often use debugging messages and logs during development and testing to diagnose issues and understand how the application is behaving. However, if these messages and logs are not properly secured and sanitized, they can be a security risk in production environments. Attackers can use this information to gain insight into the application’s inner workings and identify vulnerabilities that can be exploited.

Debugging messages and logs can contain sensitive information such as session variables, backend credentials, file and directory names, and encryption keys. Attackers can use this information to craft attacks that manipulate the application’s state and gain unauthorized access to sensitive data.

Developers should take care to ensure that debugging messages and logs are not leaked in production environments. This can include turning off debugging features or using a separate, secure logging system that is inaccessible to attackers. In addition, developers should sanitize any information that is included in debugging messages and logs to avoid exposing sensitive information.

For Practical Lab:

https://portswigger.net/web-security/information-disclosure/exploiting/lab-infoleak-on-debug-page

User account pages

By their very nature, a user’s profile or account page usually contains sensitive information, such as the user’s email address, phone number, API key, and so on. As users normally only have access to their own account page, this does not represent a vulnerability in itself. However, some websites contain logic flaws that potentially allow an attacker to leverage these pages in order to view other users’ data.

GET /user/personal-info?user=carlos

Most websites will take steps to prevent an attacker from simply changing this parameter to access arbitrary users’ account pages. However, sometimes the logic for loading individual items of data is not as robust.

We’ll look at these kind of vulnerabilities in more detail when we cover access control and IDOR vulnerabilities.

Source code disclosure via backup files

source code disclosure via backup files on a website. Access to source code makes it easier for attackers to understand the application’s behavior and construct high-severity attacks. The source code may also contain sensitive data such as API keys and credentials for accessing back-end components.

Occasionally, it is even possible to cause the website to expose its own source code. When mapping out a website, you might find that some source code files are referenced explicitly. Unfortunately, requesting them does not usually reveal the code itself. When a server handles files with a particular extension, such as .php, it will typically execute the code, rather than simply sending it to the client as text. However, in some situations, you can trick a website into returning the contents of the file instead. For example, text editors often generate temporary backup files while the original file is being edited. These temporary files are usually indicated in some way, such as by appending a tilde (~) to the filename or adding a different file extension. Requesting a code file using a backup file extension can sometimes allow you to read the contents of the file in the response.

Once an attacker has access to the source code, this can be a huge step towards being able to identify and exploit additional vulnerabilities that would otherwise be almost impossible

For Practical Lab:

https://portswigger.net/web-security/information-disclosure/exploiting/lab-infoleak-via-backup-files

Information disclosure due to insecure configuration

Websites are sometimes vulnerable as a result of improper configuration. This is especially common due to the widespread use of third-party technologies, whose vast array of configuration options are not necessarily well-understood by those implementing them.

In other cases, developers might forget to disable various debugging options in the production environment. For example, the HTTP TRACE method is designed for diagnostic purposes. If enabled, the web server will respond to requests that use the TRACE method by echoing in the response the exact request that was received. This behavior is often harmless, but occasionally leads to information disclosure, such as the name of internal authentication headers that may be appended to requests by reverse proxies.

For Practical Lab:

https://portswigger.net/web-security/information-disclosure/exploiting/lab-infoleak-authentication-bypass

Version control history

Virtually all websites are developed using some form of version control system, such as Git. By default, a Git project stores all of its version control data in a folder called .git. Occasionally, websites expose this directory in the production environment. In this case, you might be able to access it by simply browsing to /.git.

While it is often impractical to manually browse the raw file structure and contents, there are various methods for downloading the entire .git directory. You can then open it using your local installation of Git to gain access to the website’s version control history. This may include logs containing committed changes and other interesting information.

For Practical Lab:

https://portswigger.net/web-security/information-disclosure/exploiting/lab-infoleak-in-version-control-history

How to assess the severity of information disclosure vulnerabilities

Assessing the severity of information disclosure vulnerabilities depends on several factors, such as the type of information disclosed, the impact of the disclosure, and the likelihood of an attacker exploiting the vulnerability. Here are some steps that can help in assessing the severity of information disclosure vulnerabilities:

Identify the type of information disclosed: The type of information disclosed can affect the severity of the vulnerability. For example, disclosing sensitive information such as user credentials or financial data may be more severe than disclosing non-sensitive information like application version numbers.
Evaluate the potential impact: The potential impact of the information disclosure vulnerability can help determine the severity. For example, if the vulnerability allows an attacker to access sensitive information, it can have a high impact on the confidentiality, integrity, and availability of the data.
Assess the likelihood of an attacker exploiting the vulnerability: The likelihood of an attacker exploiting the vulnerability can also help determine the severity. If the vulnerability requires specific conditions or actions by an attacker, the likelihood of exploitation may be lower than a vulnerability that can be easily exploited.
Use vulnerability scoring systems: Various vulnerability scoring systems are available that can help assess the severity of information disclosure vulnerabilities, such as the Common Vulnerability Scoring System (CVSS) or the National Vulnerability Database (NVD) scoring system.
Consider the context and environment: The severity of an information disclosure vulnerability may also depend on the context and environment in which the vulnerability is present. For example, an information disclosure vulnerability in a highly sensitive system may be more severe than a similar vulnerability in a less sensitive system.

How to prevent information disclosure vulnerabilities

Preventing information disclosure completely is tricky due to the huge variety of ways in which it can occur. However, there are some general best practices that you can follow to minimize the risk of these kinds of vulnerability creeping into your own websites.

Apply the principle of least privilege: Users, applications, and systems should only have access to the data and resources they need to perform their tasks. This can limit the potential impact of an information disclosure vulnerability by reducing the amount of sensitive information that is exposed.
Implement proper access controls: Access controls should be implemented to restrict access to sensitive data and resources to authorized users only. This can include role-based access control, permission-based access control, and user authentication.
Encrypt sensitive data: Sensitive data should be encrypted both during storage and transmission to protect it from unauthorized access. This includes encrypting data at rest in databases and encrypting data in transit using secure communication protocols like HTTPS.
Regularly update and patch software: Regularly updating and patching software can help prevent information disclosure vulnerabilities by fixing security flaws in the software.
Use strong authentication mechanisms: Strong authentication mechanisms, such as multi-factor authentication and strong passwords, can help prevent unauthorized access to sensitive data.
Conduct regular vulnerability assessments and penetration testing: Regular vulnerability assessments and penetration testing can help identify potential information disclosure vulnerabilities and allow for remediation before they are exploited by attackers.
Educate employees: Employees should be educated about the risks of information disclosure vulnerabilities and trained on how to properly handle sensitive data.
Use generic error messages as much as possible. Don't provide attackers with clues about application behavior unnecessarily.
Double-check that any debugging or diagnostic features are disabled in the production environment.
Make sure you fully understand the configuration settings, and security implications, of any third-party technology that you implement. Take the time to investigate and disable any features and settings that you don't actually need.

References

PortSwigger Content : Access control vulnerabilities and privilege escalation

PortSwigger Labs : Access control vulnerabilities and privilege escalation Labs

HarabHackSploit (youtube channel) : Broken Access Control

Information Disclosure Vulnerabilities