[Affected versions]: Firefox 55.0a1 (Build Id:20170607030206) Firefox 54.0 (Build Id:20170605134926) Firefox 53.0.3 (Build Id:20170518000419) Firefox 52.2.0esr (Build Id:20170607123825) [Affected platforms]: Mac OS X 10.12.1 Windows 10 64 bit. [Unaffected platforms]: Ubuntu 16.04 64bit. [Steps to reproduce]: 1. Launch Firefox with a clean profile. 2. Click on the Pocket (or Downloads) toolbar button. 3. Fastly resize Firefox. [Expected result]: The Pocket's (or Downloads) dropdown menu is dismissed and the button is displayed as inactive. [Actual result]: The dropdown is dismissed but the button is displayed as active. [Regression range]: This seems not to be a regression since it is reproducible even with an old Firefox 45.0a1 build. [Additional notes]: For further information regarding this issue please observe the attached video.

Does this reproduce with other buttons, like the history, developer or synced tabs ones, if you move those to the toolbar?

Hi Gijs! I can reproduce this issue with almost all the buttons that have a dropdown menu (Pocket, Forget, Show Sidebars, Download, History). It seems that the only button where this issue is not reproducible is the "Show your bookmarks" button.