Open the Firefox/Nightly Health Report under 'Help' Look at the plugin display at the bottom Activated Plugins Enabled/Disabled shows incorrectly. Its reverse of reality. Tested with latest hourly m-c build on win7 x64 cset: https://hg.mozilla.org/mozilla-central/rev/a2c31dc69ab3 Not sure when Health Report page was updated as this seems to be fairly new. Maybe caused by https://bugzilla.mozilla.org/show_bug.cgi?id=866131 ?
This is caused by Bug 902075, and may be by design.