GHSA-RV3R-VQJJ-8C76

Cross-site scripting from content entered in the tags and multiselect fields

The tags and multiselect fields allow to select tags from an autocompleted list. The tags field also allows to enter new tags or edit existing tags. Kirby already handled escaping of the autocompleted tags, but unfortunately the Panel used HTML rendering for new or edited tags as well as for custom tags from the content file.

This allowed attackers with Panel access to store malicious HTML code in a tag. The browser of the victim who visited the modified page in the Panel will then have rendered this malicious HTML code.

It also allowed self-inflicted XSS attacks in the tags field (meaning that malicious code is executed in the browser of the user who entered it). This could be used in social engineering attacks where a victim is convinced by an attacker to enter malicious code into a tags field.

Visitors without Panel access could only use this attack vector if your site allows changing the content of a tags or multiselect field from a frontend form (for example user self-registration or the creation of pages from a contact or other frontend form). If you validate or sanitize the provided form data, you are already protected against such attacks by external visitors.

You are also not affected by these vulnerabilities if your site doesn't have untrustworthy users with Panel access or a way to modify field values from the frontend or if you don't use the tags or multiselect fields.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

GHSA-RV3R-VQJJ-8C76 has a CVSS score of 7.1 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.5.8.1, 3.6.6.1, 3.7.4); upgrading removes the vulnerable code path.

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The problems have been patched in Kirby 3.5.8.1, Kirby 3.6.6.1 and Kirby 3.7.4. Please update to one of these or a later version to fix the vulnerabilities.

Note: The fixes for these vulnerabilities have the side effect that values in the tags and multiselect fields that come from dynamic options are displayed with double escaping (e.g. the & character is displayed as &). In the fix for Kirby 3.5, every value in the tags field is displayed with double escaping when dynamic options are enabled, while dynamic options themselves are displayed with triple escaping. We will fix the double/triple escaping issues with a refactoring of the options fields (tags, multiselect, checkboxes, radio, select and toggles) in Kirby 3.8.

1. What is GHSA-RV3R-VQJJ-8C76? GHSA-RV3R-VQJJ-8C76 is a high-severity cross-site scripting (XSS) vulnerability in getkirby/cms (composer), affecting versions >= 3.5.7, < 3.5.8.1. It is fixed in 3.5.8.1, 3.6.6.1, 3.7.4. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is GHSA-RV3R-VQJJ-8C76? GHSA-RV3R-VQJJ-8C76 has a CVSS score of 7.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of getkirby/cms are affected by GHSA-RV3R-VQJJ-8C76? getkirby/cms (composer) versions >= 3.5.7, < 3.5.8.1 is affected.
4. Is there a fix for GHSA-RV3R-VQJJ-8C76? Yes. GHSA-RV3R-VQJJ-8C76 is fixed in 3.5.8.1, 3.6.6.1, 3.7.4. Upgrade to this version or later.
5. Is GHSA-RV3R-VQJJ-8C76 exploitable, and should I be worried? Whether GHSA-RV3R-VQJJ-8C76 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-RV3R-VQJJ-8C76 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-RV3R-VQJJ-8C76?
   • Upgrade getkirby/cms to 3.5.8.1 or later
   • Upgrade getkirby/cms to 3.6.6.1 or later
   • Upgrade getkirby/cms to 3.7.4 or later

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