At the same time, it can be used to collect sensitive information of both third-party app and users by using the following parameters (sensitive information is contained in HTTP header.),
"&response_type"=sensitive_info,token...
"&scope"=get_user_info%2Cadd_share...
It increases the likelihood of successful Open Redirect Attacks to third-party websites, too.
The vulnerabilities occurs at page "/oauth/grant?" with parameter "&redirect_uri", e.g.
Before acceptance of third-party application:
When a logged-in Renren user clicks the URL ([1]) above, he/she will be asked for consent as in whether to allow a third-party website to receive his/her information. If the user clicks OK, he/she will be then redirected to the URL assigned to the parameter "&redirect_uri".
If a user has not logged onto Renren and clicks the URL ([1]) above, the same situation will happen upon login.
After acceptance of third-party application:
A logged-in Renren user would no longer be asked for consent and could be redirected to a webpage controlled by the attacker when he/she clicks the URL ([1]).
For a user who has not logged in, the attack could still be completed after a pop-up page that prompts him/her to log in.
(2.1.1) Renren would normally allow all the URLs that belong to the domain of an authorized third-party website. However, these URLs could be prone to manipulation. For example, the "&redirect_uri" parameter in the URLs is supposed to be set by the third-party websites, but an attacker could change its value to make Attacks.
Hence, a user could be redirected from Renren to a vulnerable URL in that domain first and later be redirected from this vulnerable site to a malicious site unwillingly. This is as if the user is redirected from Renren directly. The number of Renren's OAuth 2.0 client websites is so huge that such Attacks could be commonplace.
Before acceptance of the third-party application, Renren's OAuth 2.0 system makes the redirects appear more trustworthy and could potentially increase the likelihood of successful Open Redirect Attacks of third-party website.
Once the user accepts the application, the attackers could completely bypass Renren's authentication system and attack more easily.
(2.2) Use one of webpages for the following tests. The webpage is "https://zuiyuxiang.wordpress.com/". Can suppose it is malicious and contains code that collect sensitive information of both third-party app and users.
Below is an example of a vulnerable third-party domain:
sohu.com
Vulnerable URL in this domain:
Vulnerable URL from Renren that is related to sohu.com:
POC:
