Executive Summary

This vulnerability exists in MyBB Recent threads 17.0 and is a persistent cross-site scripting (XSS) flaw. It allows attackers to inject malicious scripts by creating threads with specially crafted subject lines containing script tags. When users view the index page, the injected JavaScript executes in their browsers.

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Impact Analysis

The impact of this vulnerability is that attackers can execute arbitrary JavaScript code in the browsers of users who view the affected index page. This can lead to unauthorized actions such as stealing session cookies, redirecting users to malicious sites, or performing actions on behalf of the user without their consent.

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Compliance Impact

The vulnerability is a persistent cross-site scripting (XSS) flaw that allows attackers to inject malicious scripts into thread subject lines, which execute in the browsers of users viewing the index page.

Such XSS vulnerabilities can lead to unauthorized access to user data, session hijacking, or exposure of sensitive information, which may impact compliance with data protection regulations like GDPR or HIPAA by compromising the confidentiality and integrity of user data.

However, the provided context and resources do not explicitly discuss or analyze the impact of this vulnerability on compliance with specific standards or regulations.

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Executive Summary

CVE-2018-25309 is a persistent cross-site scripting (XSS) vulnerability in MyBB Recent Threads version 17.0. It allows attackers to inject malicious JavaScript code by creating threads with specially crafted subject lines containing script tags.

When users view the forum index page, the injected scripts execute in their browsers, potentially compromising user sessions or performing other malicious actions.

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Impact Analysis

This vulnerability can impact users by allowing attackers to execute arbitrary JavaScript in their browsers when they view the affected forum's index page.

• Attackers can hijack user sessions.
• Malicious scripts can steal sensitive information.
• It can lead to defacement or unauthorized actions performed on behalf of users.
• Because the vulnerability is persistent, the malicious code remains active until the thread is removed or the vulnerability is patched.

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Detection Guidance

This vulnerability can be detected by checking for the presence of malicious script tags in the subject lines of threads created in the MyBB Recent Threads plugin version 17.0. Since the vulnerability involves persistent cross-site scripting via thread subject parameters, inspecting thread subjects for suspicious or encoded script tags is a key detection method.

You can use commands or queries to search the database or exported thread data for occurrences of <script> tags or other suspicious JavaScript code in thread subjects.

• For example, if you have database access, you might run a SQL query like: SELECT subject FROM threads WHERE subject LIKE '%<script>%';
• Alternatively, you can use command-line tools like grep on exported data or logs: grep -i '<script>' recent_threads_data.txt

Monitoring HTTP requests and responses for injected script tags in the thread subject parameter on the index page can also help detect exploitation attempts.

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Mitigation Strategies

Immediate mitigation steps include sanitizing and validating the thread subject input to prevent script tags or other malicious code from being stored and executed.

If a patch or updated version of the MyBB Recent Threads plugin is available that fixes this vulnerability, applying that update should be the primary mitigation.

As a temporary measure, you can disable the Recent Threads plugin or restrict thread creation permissions to trusted users only to reduce the risk of exploitation.

Additionally, implementing Content Security Policy (CSP) headers can help mitigate the impact of any injected scripts by restricting script execution.

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