plone.restapi: Stored XSS by spoofing mime type

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

4.3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

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 safehtml 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:…

Published by the source

17 Jul 2026, 18:36 UTC

Last modified by the source

17 Jul 2026, 18:45 UTC

Source last checked

26 Oct 2026, 13:47 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-8rqh-vxpr-x77p

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-8rqh-vxpr-x77p

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# Patch Next advisory brief: GHSA-8rqh-vxpr-x77p

Advisory: plone.restapi: Stored XSS by spoofing mime type
IDs: GHSA-8rqh-vxpr-x77p
Record: https://patchnext.com/advisories/ghsa-8rqh-vxpr-x77p (revision 2, source checked 26 Oct 2026, 13:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: plone-restapi 10.0.1, 9.15.6. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI plone-restapi: affected < 9.15.6; >= 10.0.0, <= 10.0.0; fixed in 10.0.1, 9.15.6

## Suggested inspection (read-only)
- `python -m pip show plone-restapi`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on plone-restapi.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-8rqh-vxpr-x77p (OSV record GHSA-8rqh-vxpr-x77p lists affected ranges: PyPI plone-restapi >=0 =10.0.0 <10.0.1 (fixed))
- Verified: https://github.com/advisories/GHSA-8rqh-vxpr-x77p (GitHub-reviewed advisory GHSA-8rqh-vxpr-x77p lists affected ranges: PyPI plone-restapi >=0 =10.0.0 <=10.0.0)

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