User Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:57.0) Gecko/20100101 Firefox/57.0 Build ID: 20180103231032 Steps to reproduce: So, I'm a relatively speedy computer user and like to use a lot of keyboard shortcuts. I use the keyword feature of bookmarks to make shortcuts to websites I commonly go to. For instance typing 'f' in my address bar brings me to Facebook. Oftentimes when I load my browser, I already know that I want to go there so as soon as the browser opens, I'll Alt+D (to go to the address bar) and type 'f' followed by Enter to go to Facebook. I will often do this all before the homepage finishes loading. Similarly, this can happen if I have a link in my paste buffer that I try to go to quickly. Actual results: When the homepage loads, Firefox automatically puts the URL of that page in the address bar despite my cursor being there and me typing. This results in me accidentally going to (in the case of Google) 'fhttps://www.google.com/webhp?rls=org.mozilla:en-US:official' That page, being an invalid URL, is then brought into Search when Enter is pressed. In my case that brings me to Wikipedia, searching the above invalid link. I'll usually realize this happened and quickly try again to go to 'f', only to have the 'f' be prepended now to the Wikipedia link. Like 'fhttps://en.wikipedia.org/wiki/Special:Search?search=fhttps%3A%2F%2Fwww.google.com%2Fwebhp%3Frls%3Dorg.mozilla%3Aen-US%3Aofficial&sourceid=Mozilla-search&searchToken=9af07fssojy28c6sviuzek74p' That will then of course get searched. It's only once I slow down and let the page load, then go back to the address bar, type 'f', and press Enter, that I actually get to Facebook. Sometimes this can happen 3 or 4 times due to timing. I have attached a short video of this happening. It's fast-paced, so you may have to pause it to grasp what is going on here. Expected results: Because the cursor is in the address bar which is accepting input, the address bar should not attempt to put the loading page's URL in the address bar while my cursor is there, as it's causing a timing conflict between where I'm trying to go, and the page that is loading.

There are various bugs around about focus stealing, so ths could end up being a dupe, still it does a good job at explaining one of the most annoying use-cases. Thus, for now I'm confirming it, and eventually we can dupe later.