User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:52.0) Gecko/20100101 Firefox/52.0 Build ID: 20170317213149 Steps to reproduce: On any site with a `<select> ... <./select>` element, click that element. Actual results: the items in the select do not appear as a drop down box, they can be selected with up/down arrow Expected results: items should appear

+1 Same problem for us, with Firefox/Ubuntu and Firefox/Windows too.

Please load about:support and check if "Multiprocess Windows" is enabled. If so, please load about:config, click through the warning, and then type browser.tabs.remote in the search box, then change all prefs that starts with browser.tabs.remote.autostart to false. (You can double-click on the rows to toggle the value.) Then restart the browser (about:support should now say that Multiprocess is disabled). Does the dropdown menu work now?

FYI, we did apply what Mats proposed and we haven't seen this problem again for the last month. Though, since the problem is not easily reproducible, we can't say with certainty if it has disappeared because of the new settings or one of the Firefox updates.

Jean, thanks for the feedback. I'm going to guess this is a bug in our "e10s" implementation of the <select> dropdown menu then. Perhaps you can reset those settings now so you get "Multiprocess Windows" (e10s) again, and then report if the problem comes back? Thanks!

BTW, does the problem affect ALL sites? For example, does the problem occur with the following testcase? data:text/html,<select><option>hello

This is a pretty serious regression for <select> in e10s-enabled builds. Someone needs to look into this, and the other e10-select issues (bug 1154677) as well.

(In reply to Mats Palmgren (:mats) from comment #5) > BTW, does the problem affect ALL sites? > For example, does the problem occur with the following testcase? > data:text/html,<select><option>hello Tested this case on Win32 (FF 53.0.2) and could not reproduce: data:text/html,<select><option>hello<option>hello1<option>hello2<option>hello3<option>hello4

(In reply to Jet Villegas (:jet) from comment #7) > (In reply to Mats Palmgren (:mats) from comment #5) > > BTW, does the problem affect ALL sites? > > For example, does the problem occur with the following testcase? > > data:text/html,<select><option>hello > > Tested this case on Win32 (FF 53.0.2) and could not reproduce: > data:text/html, > <select><option>hello<option>hello1<option>hello2<option>hello3<option>hello4 Cannot reproduce on Win10 (FF 56 nightly), either.