GHSA-qvjf-922g-pj44
GHSA-qvjf-922g-pj44 is a Cross-site Scripting (XSS) vulnerability in getkirby/cms. O3 Security confirms whether GHSA-qvjf-922g-pj44 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Kirby CMS vulnerable to cross-site scripting (XSS) from links in KirbyTags and image blocks in the site frontend
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-qvjf-922g-pj44.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
getkirby/cms🐘getkirby/cmsReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
TL;DR
This vulnerability affects all Kirby sites that allow the use of the (link: …) KirbyTag, the link: parameter of the (image: …) KirbyTag, the built-in image block with a link or the HTML importer for blocks, when content is authored by users who may not be fully trusted. The attack requires an authenticated Panel user with update permission to any textarea or blocks field, or write access to content files through another vector (e.g. a frontend form or content sync pipeline). Another attack vector is the use of Html::a() or Html::link() with untrusted user input.
This vulnerability is of high severity for affected sites.
Kirby sites are not affected if none of the mentioned KirbyTags or block types are used, or if every user who can edit content is fully trusted. The attack only surfaces in the site frontend (i.e. in its templates). The Panel itself is unaffected and will not execute JavaScript that was injected into the textarea or blocks field content.
Introduction
Cross-site scripting (XSS) is a type of vulnerability that allows to execute any kind of JavaScript code inside the site frontend or Panel session of the same or other users. In the Panel, a harmful script can for example trigger requests to Kirby's API with the permissions of the victim.
In a stored XSS attack, the malicious payload is saved into the content data and has the potential to affect other users or site visitors.
Such vulnerabilities are critical if a consuming application might have potential attackers in its group of authenticated Panel users. They can escalate their privileges if they get access to the Panel session of an admin user. Depending on the site, other JavaScript-powered attacks are possible.
A specific class of stored XSS exploits the javascript: URI scheme in HTML <a href> attributes. When a browser processes a click action on a link with href="javascript:…", it executes the value as JavaScript in the origin of the current page. Because the site usually runs on the same origin as the Panel API, a successful exploit in the site frontend can give the attacker full control of the victim's Panel session.
Affected components
Kirby provides four first-party renderers that produce <a href="…"> output from editor-supplied field values:
- The
(link: …)KirbyTag - The
link:parameter of the(image: …)KirbyTag, when the parameter does not resolve to a known file or'self' - The link field of the built-in
imageblock - The HTML importer for the blocks field (which accepted the same malicious input as the
imageblock link field)
Impact
In affected releases, the underlying URL methods for these components did not filter out malicious URL values that resolve to script execution. While simple javascript: URLs were already deactivated by treating them as a relative path and prepending a single slash to the URL, the use of URLs of the format javascript://x%0A… bypasses this protection. The vbscript:, data:, livescript:, mocha: and jar: schemes are affected by the same underlying gap.
The vulnerability allows attackers to inject malicious links into content. The malicious links would then be rendered on the site frontend. If a site visitor or logged in user browsing the site would click such a link, the malicious script code would then be executed in the browser.
Patches
The problem has been patched in Kirby 4.9.1 and Kirby 5.4.1. Please update to one of these or a later version to fix the vulnerability.
In all of the mentioned releases, a new Url::hasDangerousScheme() method detects URI schemes that must never appear in a rendered href or src attribute (javascript:, vbscript:, livescript:, mocha:, jar:, data:).
Url::isAbsolute() now returns false for any URL that hasDangerousScheme() identifies as dangerous, so the URL component no longer passes these values through makeAbsolute() unchanged.
Html::link() now replaces the href with an empty string when a dangerous scheme is detected, so the rendered <a> tag links back to the current page rather than executing the injected script.
The HTML importer for blocks strips link targets with a dangerous scheme.
Due to the hardening in these underlying URL methods, the affected KirbyTags and block no longer allow dangerous schemes in link targets.
Credits
Kirby thanks @offset for responsibly reporting the identified issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | getkirby/cms | all versions | 4.9.1 |
| 🐘Packagist | getkirby/cms | ≥ 5.0.0&&< 5.4.1 | 5.4.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for getkirby/cms. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update getkirby/cms to 4.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-qvjf-922g-pj44 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-qvjf-922g-pj44 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-qvjf-922g-pj44. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-qvjf-922g-pj44 in your dependencies?
O3 detects GHSA-qvjf-922g-pj44 across Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.