GHSA-8rqh-vxpr-x77p

GHSA-8rqh-vxpr-x77p · plone.restapi: Stored XSS by spoofing mime type

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### 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. This is the same vulnerability as reported in `plone.app.textfield`: https://github.com/plone/plone.app.textfield/security/advisories/GHSA-4r4f-gg25-rmg5 ### Patches The problem has been patched: * For Plone 6.0 and 6.2, upgrade `plone.restapi` to 9.15.6. * For Plone 6.2, upgrade `plone.restapi` to 10.0.1. This will prevent abusing the REST API to store wrong rich text values. This will **not** prevent XSS from rich text fields that already have wrong values. For that, you will need a patched `plone.app.textfield` version. See the `plone.app.textfield` advisory linked above for versions. ### Workarounds There is no known workaround.

CVSS 4.3 · Medium · Fix available

Published

2026-07-17T18:36:34Z

Updated

2026-07-17T18:45:52.977215601Z

Stack: python

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