Last Thursday the OpenID foundation announced a weakness in Attribute Exchange extension.
The researchers determined that some sites were not confirming that the information passed through AX was signed. That allows an attacker to modify the information. If the site is only using AX to receive low-security information like a users self-asserted gender, then this will probably not be a problem. However if it is being used to receive information that it only trusts the identity provider to assert, then it creates the potential for an attack.
The researchers contacted the main websites impacted, and those sites have deployed a fix. OpenID Foundation board members have worked to identify other websites that were impacted and similarly have them deploy a fix. There are no known examples of attacks using this technique.
The OIDF said applications using OpenID4Java are prone to accepting unsigned attributes. OIDF advised users to update to the latest 0.9.6 version of the library. The Kay Framework was also deemed vulnerable and was patched in version 1.0.2.
There are no known exploits at this time, and the major sites that use OpenID have been contacted and have deployed a fix. For the rest of you who have applications using OpenID the recommendation is to update the OpenID4Java library to 0.9.6 final.
