Exposure of Sensitive Information to an Unauthorized Actor
membership_tool.py in Products.PlonePAS up to 4.0.12 as used in Plone before 4.2.3 and 4.3 before beta 1 allows remote attackers to enumerate user account names via a crafted URL.
CWE-200 - Information Exposure
An information exposure vulnerability is categorized as an information flow (IF) weakness, which can potentially allow unauthorized access to otherwise classified information in the application, such as confidential personal information (demographics, financials, health records, etc.), business secrets, and the application's internal environment.