Seen while looking at crash stats. Seen across all versions. https://crash-stats.mozilla.com/report/list?signature=nsXBLPrototypeHandler%3A%3AEnsureEventHandler%28nsIScriptGlobalObject*%2C%20nsIScriptContext*%2C%20nsIAtom*%2C%20nsScriptObjectHolder%26%29 Will work on correlations as none are showing up in the correlations tab at the moment. Frame Module Signature [Expand] Source 0 @0x730722f3 1 xul.dll nsXBLPrototypeHandler::EnsureEventHandler content/xbl/src/nsXBLPrototypeHandler.cpp:368 2 xul.dll nsXBLPrototypeHandler::ExecuteHandler content/xbl/src/nsXBLPrototypeHandler.cpp:316 3 xul.dll nsXBLEventHandler::HandleEvent content/xbl/src/nsXBLEventHandler.cpp:88 4 xul.dll nsEventListenerManager::HandleEventSubType content/events/src/nsEventListenerManager.cpp:1142 5 xul.dll nsEventListenerManager::HandleEventInternal content/events/src/nsEventListenerManager.cpp:1239 6 xul.dll nsEventDispatcher::Dispatch content/events/src/nsEventDispatcher.cpp:648

This has been rising up to #14 on 6.* yesterday, the comments are inconclusive, even though a few of them talk about an expired certificate, e.g.: "Getting error message when trying to open firefox: Secure Connection Failed xml.freecause.com:443 uses an invalid security certificate. The certificate expired on 9/24/2011 4:59 PM. the current time is 9/24/2011 6:19 PM. This could be a problem with the server's configutation or it could be someone trying to impersonate the server. If you have connected to this server successfully in the past the error may be tempoary and you can try again later." "freecause" is mentioned with all those comments of expired certs. Still, this is an XBL crash, and websites can AFAIK not use XBL (if they could, I was informed this crash would sound security-relevant), so I somehow suspect an add-on correlation but we don't have correlations for this signature apparently.

Here are some addons correlations from 6.0.2: 99% (674/681) vs. 4% (4346/109683) {D19CA586-DD6C-4a0a-96F8-14644F340D60} 56% (380/681) vs. 5% (5048/109683) {4ED1F68A-5463-4931-9384-8FFF5ED91D92} 27% (186/681) vs. 10% (10574/109683) {635abd67-4fe9-1b23-4f01-e679fa7484c1} (Yahoo! Toolbar, https://addons.mozilla.org/addon/2032) Looks as if this is related to McAfee ScriptScan for Firefox as well as McAfee SiteAdvisor.

Probably a different manifestation of Bug 688637, so maybe we should dupe this bug to that bug.