CVE-2021-41258: Cross-site scripting (XSS) from image block content in the site frontend
Kirby is an open source file structured CMS. In affected versions Kirby's blocks field stores structured data for each block. This data is then used in block snippets to convert the blocks to HTML for use in your templates. We recommend to escape HTML special characters to protect against cross-site scripting (XSS) attacks. The default snippet for the image block unfortunately did not use our escaping helper. This made it possible to include malicious HTML code in the source, alt and link fields of the image block, which 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 blocks field are not affected. This issue has been patched in Kirby version 3.5.8 by escaping special HTML characters in the output from the default image block snippet. Please update to this or a later version to fix the vulnerability.
Affected Software
Remediation
Patch Available
Event History
Frequently Asked Questions
What is the severity of CVE-2021-41258?
CVE-2021-41258 is considered a medium severity vulnerability due to potential implications for data integrity.
How do I fix CVE-2021-41258?
To fix CVE-2021-41258, upgrade to Kirby version 3.5.8 or later where the vulnerability is addressed.
What types of systems are affected by CVE-2021-41258?
CVE-2021-41258 affects versions of Kirby CMS from 3.5.0 to 3.5.7.1.
What impact does CVE-2021-41258 have on my website?
The vulnerability in CVE-2021-41258 could potentially allow for unauthorized HTML injection, impacting the security of your website.
Is there a workaround for CVE-2021-41258 if I can't upgrade?
While it's recommended to upgrade, you can mitigate CVE-2021-41258 by escaping HTML special characters in block data manually.