Hotfix_2001-02-23 This is a "hotfix" product. Hotfix products can be installed to incorporate modifications to Zope at runtime without requiring an immediate installation upgrade. Hotfix products are installed just as you would install any other Zope product. This hotfix addresses and important security issue that affects Zope versions up to and including Zope 2.3.1 b1. The issue is related to ZClasses in that a user with through-the-web scripting capabilities on a Zope site can view and assign class attributes to ZClasses, possibly allowing them to make inappropriate changes to ZClass instances. This patch also fixes problems in the ObjectManager, PropertyManager, and PropertySheet classes related to mutability of method return values which could be perceived as a security problem. We *highly* recommend that any Zope site running versions of Zope up to and including 2.3.1 b1 have this hotfix product installed to mitigate these issues if the site is accessible by untrusted users who have through-the-web scripting privileges.