Описание
plone.app.textfield: Stored XSS by spoofing mime type
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:
- For Plone 6.0, upgrade
plone.app.textfieldto 2.0.2. - For Plone 6.1, upgrade
plone.app.textfieldto 3.0.2. - For Plone 6.2, upgrade
plone.app.textfieldto 4.0.1.
Workarounds
There is no known workaround.
Пакеты
plone.app.textfield
< 2.0.2
2.0.2
plone.app.textfield
>= 3.0.0, < 3.0.2
3.0.2
plone.app.textfield
= 4.0.0
4.0.1
Связанные уязвимости
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.