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GHSA-4r4f-gg25-rmg5

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

Source: GitHub Advisory Database (reviewed) Moderate CVE-2026-54503

Packages

EcosystemPackageAffectedFixed in
PyPI plone.app.textfield < 2.0.2 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

Details

As written in the advisory (Markdown source, shown as plain text).

### 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.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. ### Workarounds There is no known workaround.

References

External links from the advisory. They lead to third-party sites.