In 2010, OWASP added "Unvalidated Redirects and Forwards" to its Top 10 list and merged it into "Sensitive Data Exposure" in 2013 [owasp1] [owasp2]. Open redirects are often overlooked, and their impact is not always well understood. At first, it does not look like a big deal. The user is receiving a 3xx status code and is being redirected to another URL. That target URL should handle all authentication and access control, regardless of where the data originated.