GHSA-v8m4-3w37-ghxx: 
PHP vulnerability analysis and mitigation

A Cross-Site Scripting (XSS) vulnerability was discovered in TYPO3 CMS's Form Framework validation handling, identified on December 17, 2019. The vulnerability affects TYPO3 CMS versions 8.0.0-8.7.29, 9.0.0-9.5.11, and 10.0.0-10.2.0. This security issue was assigned a moderate severity rating with a CVSS v3.1 base score of 6.1 (TYPO3 Advisory, GitHub Advisory).

The vulnerability exists in the output of field validation errors in the Form Framework component of TYPO3 CMS. The issue has been classified with CVSS v3.1 metrics indicating a Network attack vector, Low attack complexity, No privileges required, and Required user interaction. The scope is Changed, with Low impact on both Confidentiality and Integrity, and No impact on Availability (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N). The vulnerability is tracked as CWE-79, which is a common identifier for Cross-Site Scripting issues (GitHub Advisory).

The vulnerability could allow attackers to execute cross-site scripting attacks through the Form Framework validation handling mechanism. This could potentially lead to unauthorized data access and modification, affecting both the confidentiality and integrity of the system (TYPO3 Advisory).

Users are advised to update to the patched versions: TYPO3 8.7.30, 9.5.12, or 10.2.1. These versions contain the necessary security fixes to address the XSS vulnerability (TYPO3 Advisory).