--- title: "TYPO3-CORE-SA-2021-008: Cross-Site Scripting in Content Preview" url: "https://news.typo3.com/security/advisory/typo3-core-sa-2021-008" description: It has been discovered that TYPO3 CMS is vulnerable to cross-site scripting. image: "https://news.typo3.com/_assets/d1e01514e4c4a5b3147940fa2ec50682/Images/og-image-news.jpg" date: 2026-06-11 modified: 2026-06-11 categories: - "Developer & Technology" - "Product Updates & Roadmap" - TYPO3 CMS --- # TYPO3-CORE-SA-2021-008: Cross-Site Scripting in Content Preview - [Developer & Technology](https://news.typo3.com/article/category/developer-technology) - [Product Updates & Roadmap](https://news.typo3.com/article/category/product-updates-roadmap) - Security / [TYPO3 CMS](https://news.typo3.com/article/category/security/typo3-cms) TYPO3-CORE-SA-2021-008: Cross-Site Scripting in Content Preview =============================================================== 16 March 2021 ![A laptop screen displaying a list of security advisories](https://news.typo3.com/typo3temp/assets/_processed_/d/c/csm_security_blog_default_77f8e86036.webp) It has been discovered that TYPO3 CMS is vulnerable to cross-site scripting. - ![](https://news.typo3.com/typo3temp/assets/t3g/blog/gravatar/b8266fdc667b773926c59081862ab148.jpeg)[Oliver Hader](https://news.typo3.com/article/author/oliver-hader) - **Component Type:** TYPO3 CMS - **Subcomponent:** Content Preview Renderer (ext:backend) - **Release Date:** March 16, 2021 - **Vulnerability Type:** Cross-Site Scripting - **Affected Versions:** 7.0.0-7.6.50, 8.0.0-8.7.39, 9.0.0-9.5.16, 10.0.0-10.4.1, 11.0.0-11.1.0 - **Severity:** Medium - **Suggested CVSS:** [CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N/E:F/RL:O/RC:C](https://nvd.nist.gov/vuln-metrics/cvss/v3-calculator?vector=AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N/E:F/RL:O/RC:C&version=3.1) - **References:** [CVE-2021-21370](https://nvd.nist.gov/vuln/detail/CVE-2021-21370), [CWE-79](https://cwe.mitre.org/data/definitions/79.html) ### Problem Description It has been discovered that content elements of type menu are vulnerable to cross-site scripting when their referenced items get previewed in the page module. A valid backend user account is needed to exploit this vulnerability. The affected code is only executed if an extension is used that actually leverages the type menu. By default this is not available by the Core. ### Solution Update to TYPO3 versions 7.6.51, 8.7.40, 9.5.25, 10.4.14, 11.1.1 that fix the problem described. ### Credits Thanks to TYPO3 contributor Oliver Bartsch who reported and fixed the issue. ### General Advice Follow the recommendations that are given in the [TYPO3 Security Guide](https://docs.typo3.org/typo3cms/CoreApiReference/Security/Index.html#security). Please subscribe to the [typo3-announce](http://lists.typo3.org/cgi-bin/mailman/listinfo/typo3-announce) mailing list. ### General Note All security related code changes are tagged so that you can easily look them up in our [review system](https://review.typo3.org/#/q/status:merged+project:Packages/TYPO3.CMS+topic:security,n,z). ![](https://news.typo3.com/typo3temp/assets/t3g/blog/gravatar/cc7cba9757f98fbe05023a139119df74.jpeg) About the Author [Oliver Hader](https://news.typo3.com/article/author/oliver-hader) Core Developer at TYPO3 GmbH,Hof, Germany [Website](https://typo3.com)[Twitter](https://twitter.com/ohader)[LinkedIn](https://www.linkedin.com/in/oliverhader/)[Xing](https://www.xing.com/profile/Oliver_Hader) Oliver started to work with TYPO3 in 2005 and was fascinated by the product and its universe. Since 2007 he is member of the TYPO3 Core Team. After going back to university in 2014 for achieving a postgraduate master degree in internet web science, he is now researching on advanced web technology topics in general and for TYPO3 in particular. In his spare time, Oliver loves to go cycling cross-country in the uplands around Hof (Germany) in northern Bavaria - at the region where he's living as well. [More posts by this author](https://news.typo3.com/article/author/oliver-hader)