Covert redirect is a security flaw that allows attackers to exploit an open redirect vulnerability.
Open redirects are a failure to check that a redirected URL is a valid one. The covert redirect attacker takes advantage of that weakness to pop up a fraudulent login window, subsequently stealing the login info and redirecting the user to a page that installs malware for more criminal purposes, such as identity theft.
Covert redirect was discovered by PhD student Wang Jing from Nanyang Technological University in June 2014. Wang Jinf's site, tetraph.com, claimed to demonstrate a vulnerability that affected major sites including Facebook, Google, Yahoo and Microsoft using Oauth and OpenID. According to Jing, the vulnerability enabled open redirect by stealing an Oauth token.
Contrary to initial reports, experts say covert redirect is not a Oauth- and OpenID-specific flaw but is more a problem of how security is handled in conjunction with enabling open redirect to third-party websites.