CVE-2021-21365: TYPO3

Medium severity, CVSS 5.4. EPSS: 0.9% chance of exploitation in the next 30 days.

Bootstrap Package is a theme for TYPO3. It has been discovered that rendering content in the website frontend is vulnerable to cross-site scripting. A valid backend user account is needed to exploit this vulnerability. Users of the extension, who have overwritten the affected templates with custom code must manually apply the security fix. Update to version 7.1.2, 8.0.8, 9.1.4, 10.0.10 or 11.0.3 of the Bootstrap Package that fix the problem described. Updated version are available from the TYPO3 extension manager, Packagist and at https://extensions.typo3.org/extension/download/bootstrap_package/.

Affected products

• TYPO3 TYPO3: before 7.1.2 (fixed in 7.1.2); from 8.0.0, before 8.0.8 (fixed in 8.0.8); from 9.0.0, before 9.0.4 (fixed in 9.0.4); from 9.1.0, before 9.1.3 (fixed in 9.1.3); from 10.0.0, before 10.0.10 (fixed in 10.0.10); from 11.0.0, before 11.0.3 (fixed in 11.0.3)

Published 2021-04-27. Last modified 2026-06-17.