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

Summary

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.

Timeline

1. Sep 15, 2026, 4:38 PM UTCCVE published
2. Sep 15, 2026, 7:02 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Sep 15, 2026, 7:02 PM UTCRecord last updated

Affected versions

• 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-textfieldPyPI

  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-textfieldPyPI

  fixed in 2.0.2

• plone-app-textfieldPyPI

  From 3.0.0 · fixed in 3.0.2

• plone-app-textfieldPyPI

  From 4.0.0 · fixed in 4.0.1

References 4