medium

CVE-2026-54503

PyPI · plone.app.textfield

Summary

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

Severity
medium
CVSS
4.3
EPSS
0.4% (p34)
CWE
CWE-80
Also known as
GHSA-4r4f-gg25-rmg5
Published
2026-07-17
Updated
2026-07-17

Advisory details

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:

Workarounds

There is no known workaround.

References

Related advisories

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Sources: CISA KEV (public domain), OSV.dev & GitHub Advisory Database (CC-BY-4.0), FIRST EPSS, NVD/CWE (public domain). Served live from the Stateward advisory database.