plone.app.portlets Vulnerable to Remote Code Execution via TALES Injection

Summary

plone.app.portlets.portlets provides a Plone-specific user interface for plone.portlets, as well as a standard set of portlets that ship with Plone. Starting in version 5.0.0 and prior to versions 5.0.8, 6.0.4, and 7.0.2, the Classic portlet (plone.app.portlets.portlets.classic) used its user-supplied template/macro fields to build a TALES path expression that was then evaluated by the TAL path() helper. Because the value was interpreted as a full TALES expression, a user able to add or edit a Classic portlet could supply a crafted value that escapes simple path traversal and is evaluated as arbitrary code. This is exploitable by any authenticated user who can configure a Classic portlet - which, with the default role map, includes regular users on their personal dashboard. The result is code execution in the context of the Plone process, i.e. a privilege escalation across the trust boundary between an authenticated web user and the server-side process. The problem has been patched in `plone.app.portlets` 5.0.8, 6.0.4, and 7.0.2. Some workarounds are available. Restrict who can manage portlets: remove the `plone.app.portlets.ManageOwnPortlets` permission from untrusted roles, and limit Manage portlets to trusted administrators (usually this is already restricted to the Manager and Site Administrator roles). Where the Classic portlet is not needed, unregister it so it cannot be added. This would need to be done by editing a `portlets.xml` in your own code. One may also effectively disable showing the classic portlet by customising its template. In the Zope Management Interface go to the `portal_view_customizations` tool, locate the `classic.pt` template and click it. Click the Customize button. Remove all text and replace it with `<div>The classic portlet was disabled.</div>`. (This is not a recommended way of customizing a template, but in this case it is quite effective.)