Reproducible on: Firefox 41.0a1 and Firefox 40.0a2 across all platforms Prerequisites: create xpinstall.signatures.dev-root pref and set it to true 1.Launch Firefox with clean profile 2.Go to https://addons-dev.allizom.org/en-US/firefox/addon/video-downloadhelper/?src=cb-dl-users 3.Click ”Add to Firefox” green button 4.Click “Allow” button 5.After the add-on is downloaded and verified, click “Install” button 6.In the last doorhanger click “x” button which corresponds to sync section in order to close this box. ( http://i.imgur.com/diNWY6n.jpg ) 7.Repeat steps 3,4 and 5 for another add-on installation ( e.g https://addons-dev.allizom.org/en-US/firefox/addon/firebug/?src=cb-dl-users ) 8.Check the Sync section from the last add-on confirmation doorhanger ( http://i.imgur.com/MDeXsMc.jpg ) ER Sync doorhanger appears for each add-on install process. AR Sync doorhanger is no longer displayed for any install process once it has been closed. Additional notes: - This issue is reproducible on Firefox 41.0a1 (2015-05-20) and 40.0a2 (2015-05-20) using Windows 7 64-bit, Ubuntu 14.04 64-bit and Mac OS X 10.9.5.
Looks like probably fallout from bug 1162584
Sorry misread this. If you click the symc promo close button then it's not meant to show up again, see bug 618913 comment 7.