Stored XSS in K2 Component for Joomla

Detection Guidance

The vulnerability in K2 ≤ 2.26 involves the `#__k2_users.image` column being rendered directly into HTML src attributes without HTML escaping, which can be detected by inspecting the HTML output of affected pages for unescaped user image data.

To detect this on your system, you can review the HTML source of pages that display user images via K2 templates and look for suspicious or unescaped content in the src attributes.

There are no specific commands provided in the available resources to detect this vulnerability automatically.

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Executive Summary

The vulnerability in K2 versions up to 2.26 involves the `#__k2_users.image` column being rendered directly into HTML `src` attributes through two different templates without applying HTML escaping.

This means that user-supplied data in the image column can be injected into the HTML source attribute as-is, potentially allowing malicious content to be executed or displayed.

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Impact Analysis

Because the image data is rendered without HTML escaping, an attacker could inject malicious code or content into the image source attribute.

This could lead to security issues such as cross-site scripting (XSS), which may allow attackers to execute scripts in the context of the affected website, potentially compromising user data or site integrity.

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Mitigation Strategies

Immediate mitigation steps include updating K2 to a version later than 2.26 where this vulnerability is fixed.

If an update is not immediately possible, review and modify the affected templates to ensure proper HTML escaping of the `#__k2_users.image` column before rendering it into HTML src attributes.

Additionally, restrict user input and sanitize any data that could be injected into the image fields to prevent exploitation.

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