Yo 1.1 - 1.3.1 - Unauthenticated SQL Injection via username Parameter

The Yo WordPress plugin from 1.1 through 1.3.1 does not sanitize or parameterize the username request parameter before using it in a SQL query, and reads it before WordPress applies its request escaping, allowing unauthenticated attackers to perform SQL injection and read arbitrary database contents including administrator password hashes.