CVE-2026-54503
MEDIUMCVE-2026-54503 is a medium-severity (CVSS 4.3) vulnerability in plone-app-textfield. O3 Security confirms whether CVE-2026-54503 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
plone.app.textfield: Stored XSS by spoofing mime type
Real-World Exposure
plone-app-textfield🐍plone-app-textfield🐍plone-app-textfieldReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
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.
Patches
The problem has been patched:
- For Plone 6.0, upgrade
plone.app.textfieldto 2.0.2. - For Plone 6.1, upgrade
plone.app.textfieldto 3.0.2. - For Plone 6.2, upgrade
plone.app.textfieldto 4.0.1.
Workarounds
There is no known workaround.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | plone-app-textfield | all versions | 2.0.2 |
| 🐍PyPI | plone-app-textfield | ≥ 3.0.0&&< 3.0.2 | 3.0.2 |
| 🐍PyPI | plone-app-textfield | ≥ 4.0.0&&< 4.0.1 | 4.0.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for plone-app-textfield. 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 plone-app-textfield to 2.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54503 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 CVE-2026-54503 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 CVE-2026-54503. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-54503 in your dependencies?
O3 detects CVE-2026-54503 across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.