Reproducible on: * Firefox 39.0 RC (build6: 20150630154324) - intermittently * Aurora 40.0a2 (2015-06-29) * Nightly 42.0a1 (2015-07-01) Affected platforms: * Windows 10 Pro (x64) Insider Preview Build 10158 * Windows 8.1 Pro (x64) - intermittently * Windows 7 (x64) - intermittently Steps to reproduce: 1. Launch Firefox. 2. Press [F11] to enter full screen. 3. Position the mouse cursor at the top or top corners of the screen to make the window controls / title bar (e.g. minimize, maximize, etc.) visible. Expected result: The title bar along with the window controls are visible if the cursor is positioned at the top of the screen. Actual result: * On Windows 10, the user is unable to bring up the title bar once he enters full screen. The only way to exit full screen is by pressing [F11] once again. * On Windows 8.1 / 7, the same behavior occurs but intermittently (read rarely). Most of the times, the title bar/window controls are made visible. Additional notes: * This doesn't seem to be a recent regression but it occurs more often on Windows 10 than other.

I tested on Windows 10 Pro Insider Preview Build 10162 (x64) with Nightly 42.0a1 (2015-07-06), but I cannot reproduce this issue with the STR in comment 0. Not sure what's wrong there.

(In reply to Xidorn Quan [:xidorn] (UTC+12) from comment #1) > I tested on Windows 10 Pro Insider Preview Build 10162 (x64) with Nightly > 42.0a1 (2015-07-06), but I cannot reproduce this issue with the STR in > comment 0. Not sure what's wrong there. I'm also having trouble reproducing this on Build 10162. Tried with a Microsoft Surface Pro 2 and also with my regular desktop PC, with no luck.

I can't reproduce this either. Calling it a P4 based on it being pre-existing and hard to reproduce, but if someone can figure out how to trigger this more reliably it would be helpful (and probably increase priority).

Resolving WFM based on the comments.