User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:37.0) Gecko/20100101 Firefox/37.0 Build ID: 20150402191859 Steps to reproduce: Type in searches in search box and hit enter. Actual results: 1) Uses random search instead of default search (Google) or 2) A window pops up asking me to select my default search engine when I already have. or 3) Works as it should, giving me the default Google search. There is no discernible pattern to which it does. Expected results: My default (Google search) should run.

Does this also happen when you start Firefox in a brand new profile? https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles

I'm experiencing the same issue, FF 37.0.1

Is it really random or is it doing what your mouse cursor is hovering over? For me, it seems that the 'Enter' key is being caught by the button mouseover instead of the text box.

Confirming. If the mouse happens to be over the place where one of the buttons in the search box pops up, and the user types into the box, we switch search engines, which is extremely confusing. I guess executing the search with enter should not take the mouse hover into account.

Attempt at a better description.

This looks like a duplicate of Bug 1139655 - mouse over search engine changes search engine (too easy to inadvertently use different engine for searches)

Not really. There's also bug 1113731 which is even closer to this one, but the STR between the 3 are all subtly different.

This issue is still present. If the mouse is hovering over a search provider icon, or the "Change Search Settings" button, pressing Enter behaves exactly the same as a mouse click. Interestingly, this does not happen for the toolbar search bar, but only for the search bar on about:home/about:newtab.