Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Firefox/38.0 Mozilla/5.0 (Windows NT 6.3; rv:38.0) Gecko/20100101 Firefox/38.0 Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:38.0) Gecko/20100101 Firefox/38.0 Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Firefox/38.0 Steps to reproduce: 1. Open Firefox (e10s enabled) 2. Open a new tab and (optional) navigate to any website 3. Drag the new tab to desktop Expected Results: The tab is opened and correctly displayed in a new window. Actual Results: The tab remains displayed in the old window but it can't be closed (until the browser is closed). The new window is blank (so the tab is not displayed). Notes: This is an e10s specific issue, it doesn't reproduce with e10s disabled. Same thing happens when right click on the tab -> Move to new window. This issue is not a regression.

Does this actually happen with "any website"? This seems like a dupe of bug 1094328 otherwise.

It indeed affects only XUL tabs, so this is a dupe. Thanks for the heads up!