It was reported [1] that Plone suffers from a vulnerability that can be exploited to bypass certain security restrictions. This is due to a vulnerable bundled version of Zope.
Plone 3.x users that backported the fix for CVE-2011-0720 (PloneHotfix20110720) are affected due to the vulnerability being inadvertently backported via the hotfix.
A new hotfix (20110622) is available [2] to correct the flaw.
[1] http://plone.org/products/plone/security/advisories/20110622 [2] http://plone.org/products/plone-hotfix/releases/20110622
Plone upstream has published a pre-announcement about a security flaw, present in Zope v2.12.x and Zope v2.13.x, which could allow execution of arbitrary code by anonymous users. An authenticated attacker could provide a specially-crafted web page, which once visited by an unsuspecting Zope user would lead to arbitrary commands execution with the privileges of the Zope/Plone service.
References: [1] http://plone.org/products/plone/security/advisories/20110928 [2] http://secunia.com/advisories/46221/
Note: The vendor announced the final version of the advisory and the patch to be available at 2011-10-04 15:00 UTC at the following location: [3] http://plone.org/products/plone/security/advisories/20110928
Cross-site scripting (XSS) vulnerability in ZMI pages that use the managetabsmessage in Zope 2.11.4, 2.11.2, 2.10.9, 2.10.7, 2.10.6, 2.10.5, 2.10.4, 2.10.2, 2.10.1, 2.12.
Cross-site scripting (XSS) vulnerability in Zope 2.8.x before 2.8.12, 2.9.x before 2.9.12, 2.10.x before 2.10.11, 2.11.x before 2.11.6, and 2.12.x before 2.12.3, 3.1.1 through 3.4.1. allows remote attackers to inject arbitrary web script or HTML via vectors related to the way error messages perform sanitization. NOTE: this issue exists because of an incomplete fix for CVE-2010-1104