An open redirect is a vulnerability that exists when a script allows redirection to an external site by directly calling a specific URL in an unfiltered,unmanaged fashion. A similar vulnerability is reported in Google by “Ucha Gobejishvili (longrifle0x)”. This problem may assist an attacker to conduct phishing attacks, trojan distribution, spammers and spammers. Same vulnerability in Facebook, Discovered by ZeRtOx from Devitel group:https://www.facebook.com/l.php?h=5AQH8ROsPAQEOTSTw7sgoW1LhviRUBr6iFCcj4C8YmUcC8A&u=www.something
Source: https://thehackernews.com/2012/01/url-redirection-vulnerability-in-google.html