HTML sanitizer is written in PHP, aiming to provide XSS-safe markup based on explicitly allowed tags, attributes and values. In versions prior to 1.5.0 or 2.1.1, malicious markup used in a sequence with special HTML CDATA sections cannot be filtered and sanitized due to a parsing issue in the upstream package masterminds/html5. This allows bypassing the cross-site scripting mechanism of typo3/html-sanitizer. The upstream package masterminds/html5 provides HTML raw text elements (script, style, noframes, noembed and iframe) as DOMText nodes, which were not processed and sanitized further. None of the mentioned elements were defined in the default builder configuration, that's why only custom behaviors, using one of those tag names, were vulnerable to cross-site scripting. This issue has been fixed in versions 1.5.0 and 2.1.1.
GHSA-47m6-46mj-p235: By-passing Cross-Site Scripting Protection in HTML Sanitizer
### CVSS: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N/E:F/RL:O/RC:C (4.4)
Problem Due to an encoding issue in the serialization layer, malicious markup nested in a noscript element was not encoded correctly. noscript is disabled in the default configuration, but might have been enabled in custom scenarios. This allows bypassing the cross-site scripting mechanism of typo3/html-sanitizer.
Solution Update to typo3/html-sanitizer versions 1.5.1 or 2.1.2 that fix the problem described.
Credits Thanks to David Klein and Yaniv Nizry who reported this issue, and to TYPO3 security team members Oliver Hader and Benjamin Franzke who fixed the issue.
References TYPO3-CORE-SA-2023-002
### CVSS: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N/E:F/RL:O/RC:C (4.4)
Problem DOM processing instructions are not handled correctly. This allows bypassing the cross-site scripting mechanism of typo3/html-sanitizer.
Solution Update to typo3/html-sanitizer versions 1.5.3 or 2.1.4 that fix the problem described.
Credits Thanks to Yaniv Nizry and Niels Dossche who reported this issue, and to TYPO3 core & security team member Oliver Hader who fixed the issue.
References TYPO3-CORE-SA-2023-007 Context & Details at masterminds/html5