Silent Breach finds a vulnerability with the online Wikipedia web site and in its free open source MediaWiki platform:

This vulnerability allows an attacker to gather information on the target (Wikipedia.org) and more easily narrow down potential breaches in the modules used by this web site. This kind of vulnerability is commonly referred to as Information Exposure Through Sent Data (Weakness classification id: CWE-201).

Silent Breach has contacted the Wikipedia.org team to remedy this issue before the full details of this 0-day can be disclosed.