Description
WordPress is prone to multiple username enumeration weaknesses because it displays different responses to requests depending on whether or not the username exists. Attackers may exploit these weaknesses to discern valid usernames, which may aid them in brute-force password cracking or other attacks. WordPress versions prior to 2.8.1 are vulnerable.
Remediation
Update to WordPress version 2.8.1 or latest
References
http://www.coresecurity.com/content/WordPress-Privileges-Unchecked
Related Vulnerabilities
WordPress 4.6.x PHP Object Injection (4.6 - 4.6.20)
CakePHP Exposure of Sensitive Information to an Unauthorized Actor Vulnerability (CVE-2011-3712)
Apache HTTP Server Configuration Vulnerability (CVE-2009-1195)
WordPress Plugin FV Flowplayer Video Player Cross-Site Scripting (6.6.4)
WordPress Plugin Modern Events Calendar Arbitrary File Upload (7.11.0)