GHSA-g4c2-ghfg-g5rh

### Impact Plone is vulnerable to reflected cross site scripting and open redirect when an attacker can get a compromised version of the image_view_fullscreen page in a cache, for example in Varnish. The technique is known as cache poisoning. Any later visitor can get redirected when clicking on a link on this page. Usually only anonymous users are affected, but this depends on your cache settings. ### Patches A new version 3.0.6 of Products.ATContentTypes has been released with a fix. This version works on Plone 5.2 (Python 2 only) and will be included in Plone 5.2.7. Note that the Products.CMFPlone package has the same problem in the 4.3 series. `plone.app.contenttypes` has the same problem in all versions, see [advisory](https://github.com/plone/plone.app.contenttypes/security/advisories/GHSA-f7qw-5fgj-247x). For all unpatched versions of the three packages, you can use the following workaround. ### Workaround Make sure the image_view_fullscreen page is not stored in the cache. In Plone: * Login as Manager and go to Site Setup. * Go to the 'Caching' control panel. If this does not exist, or 'Enable caching' is not checked, you should normally not be vulnerable. * Click on the tab 'Caching operations'. * Under 'Legacy template mappings' locate the ruleset 'Content item view'. * From the last column ('Templates') remove 'image_view_fullscreen'. * Click on Save. ### Reporter This vulnerability was responsibly disclosed to the Plone Security Team by Gustav Hansen, F-Secure Consulting. Thank you! ### For more information If you have any questions or comments about this advisory, email us at [[email protected]](mailto:[email protected]) This is also the correct address to use when you want to report a possible vulnerability. See [our security report policy](https://plone.org/security/report).