CVE-2026-54503

plone.app.textfield: Stored XSS by spoofing mime type

Workarounds

There is no known workaround.

A stored XSS affecting RichText fields. RichTextValue.output returns the raw, unsanitized stored value whenever the stored mimeType equals the outputMimeType. Because the safe-HTML output type (text/x-html-safe) is the type that signifies "already sanitized", any value whose stored mimeType equals it bypasses the safe_html transform entirely on render. The transform itself is sound, it correctly strips on* event-handler attributes and javascript:/data: URIs; the defect is that it is never invoked for these values. The unsanitized value is then emitted via tal:content="structure ...", which performs no escaping, so the payload executes in the viewer's browser.

This can be a problem when a RichText field is wrongly defined in code with a mimeType and outputMimeType that are the same, or when the REST API is used to the same effect.

CVE-2026-54503 has a CVSS score of 4.3 (Medium). 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 (2.0.2, 3.0.2, 4.0.1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

The problem has been patched:

• For Plone 6.0, upgrade plone.app.textfield to 2.0.2.
• For Plone 6.1, upgrade plone.app.textfield to 3.0.2.
• For Plone 6.2, upgrade plone.app.textfield to 4.0.1.

1. What is CVE-2026-54503? CVE-2026-54503 is a medium-severity security vulnerability in plone.app.textfield (pip), affecting versions < 2.0.2. It is fixed in 2.0.2, 3.0.2, 4.0.1.
2. How severe is CVE-2026-54503? CVE-2026-54503 has a CVSS score of 4.3 (Medium). 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 plone.app.textfield are affected by CVE-2026-54503? plone.app.textfield (pip) versions < 2.0.2 is affected.
4. Is there a fix for CVE-2026-54503? Yes. CVE-2026-54503 is fixed in 2.0.2, 3.0.2, 4.0.1. Upgrade to this version or later.
5. Is CVE-2026-54503 exploitable, and should I be worried? Whether CVE-2026-54503 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 CVE-2026-54503 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 CVE-2026-54503?
   • Upgrade plone.app.textfield to 2.0.2 or later
   • Upgrade plone.app.textfield to 3.0.2 or later
   • Upgrade plone.app.textfield to 4.0.1 or later