CVE-2021-41252

Kirby is an open source file structured CMS ### Impact Kirby's writer field stores its formatted content as HTML code. Unlike with other field types, it is not possible to escape HTML special characters against cross-site scripting (XSS) attacks, otherwise the formatting would be lost. If the user is logged in to the Panel, a harmful script can for example trigger requests to Kirby's API with the permissions of the victim. Because the writer field did not securely sanitize its contents on save, it was possible to inject malicious HTML code into the content file by sending it to Kirby's API directly without using the Panel. This malicious HTML code would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site. Attackers must be in your group of authenticated Panel users in order to exploit this weakness. Users who do not make use of the writer field are not affected. This issue has been patched in Kirby 3.5.8 by sanitizing all writer field contents on the backend whenever the content is modified via Kirby's API. Please update to this or a later version to fix the vulnerability.

• CWE-79

• https://github.com/getkirby/kirby/commit/25fc5c6b330442e6433c99befc688f3698c5d1fcPatch, Third Party Advisory
• https://github.com/getkirby/kirby/releases/tag/3.5.8Release Notes, Third Party Advisory
• https://github.com/getkirby/kirby/security/advisories/GHSA-x7j7-qp7j-hw3qThird Party Advisory
• https://github.com/getkirby/kirby/commit/25fc5c6b330442e6433c99befc688f3698c5d1fcPatch, Third Party Advisory
• https://github.com/getkirby/kirby/releases/tag/3.5.8Release Notes, Third Party Advisory
• https://github.com/getkirby/kirby/security/advisories/GHSA-x7j7-qp7j-hw3qThird Party Advisory

Published

Nov 16, 2021

Last Modified

Jun 17, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2021-41247JupyterHub is an open source multi-user server for Jupyter n…7.5
• CVE-2021-41248GraphiQL is the reference implementation of this monorepo, G…4.7
• CVE-2021-41249GraphQL Playground is a GraphQL IDE for development of graph…4.7
• CVE-2021-4125It was found that the original fix for log4j CVE-2021-44228 …8.1
• CVE-2021-41250Python discord bot is the community bot for the Python Disco…4.3
• CVE-2021-41251@sap-cloud-sdk/core contains the core functionality of the S…5.9
• CVE-2021-41253Zydis is an x86/x86-64 disassembler library. Users of Zydis …8.1
• CVE-2021-41254kustomize-controller is a Kubernetes operator, specialized i…8.8
• CVE-2021-41256nextcloud news-android is an Android client for the Nextclou…7.1
• CVE-2021-41258Kirby is an open source file structured CMS. In affected ver…5.4
• CVE-2021-41259Rejected reason: DO NOT USE THIS CANDIDATE NUMBER. ConsultID…
• CVE-2021-4126When receiving an OpenPGP/MIME signed email message that con…6.5