Security researcher Muneaki Nishimura reported that navigator.sendBeacon() does not follow the cross-origin resource sharing (CORS) specification. This results in the request from sendBeacon() lacking an origin header in violation of the W3C Beacon specification and not being treated as a CORS request. This allows for a potential Cross-site request forgery (XSRF) attack from malicious websites.

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


External Reference:

http://www.mozilla.org/security/announce/2015/mfsa2015-03.html


Acknowledgements:

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