N/A

CVSS Score

-

CVSS Score

Basic Information

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CVE-2025-54476

CVE-2025-54476: Joomla! CMS vulnerable to XSS via the input filter

Improper handling of input could lead to a cross-site scripting (XSS) vector in the checkAttribute method of the input filter framework class.

(GitHub Advisory)

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CVE-2025-54476

CVE-2025-54476:

N/A

CVSS Score

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
joomla/filter	composer	= 4.0.0	4.0.1
joomla/filter	composer	>= 3.0.0, < 3.0.5	3.0.5
joomla/filter	composer	< 2.0.6	2.0.6

Technical Details

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Root Cause Analysis

The vulnerability lies in the checkAttribute method of the Joomla\Filter\InputFilter class. The provided patches clearly show that this function was modified to mitigate an XSS vulnerability. The core of the vulnerability is that the function failed to account for whitespace and other non-printable characters that could be used to obfuscate malicious JavaScript in HTML attributes. An attacker could craft an input like <img src="java\tscript:alert('xss')">, which would bypass the original filter. The patch adds a line of code to strip these characters from the attribute value before it is checked for dangerous content. This directly points to checkAttribute as the vulnerable function. The other modified files are test cases that confirm the fix by adding new tests for the previously successful XSS vectors.

Vulnerable functions

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WAF Protection Rules

WAF Rule

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Reasoning

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