Security researcher Xiaofeng Zheng of the Blue Lotus Team at Tsinghua University reported reported that a Web Proxy returning a 407 Proxy Authentication response with a Set-Cookie header could inject cookies into the originally requested domain. This could be used for session-fixation attacks. This attack only allows cookies to be written but does not allow them to be read.

In general this flaw cannot be exploited through email in the Thunderbird product, but is potentially a risk in browser or browser-like contexts.


External Reference:

http://www.mozilla.org/security/announce/2015/mfsa2015-04.html


Acknowledgements:

Red Hat would like to thank the Mozilla project for reporting this issue. Upstream acknowledges Xiaofeng Zheng as the original reporter.