Original report: http://bugs.debian.org/598760 from Felipe Ignacio Cañas Sabat. It is easily reproducible with 2.30.6.

“When a tab with a textfield that receives focus on page load finishes to load,
said textfield will receive focus even if the tab is not selected. The recently
loaded tab, however, is NOT selected, so the effect is quite confusing.

Two ways to trigger:

I. When typing into the address bar
1. On a new tab, enter the address of a page with an autofocusing textfield,
like google
2. Before the page loads, open another tab and start typing on the address bar

I would expect to see what I type being entered into the address bar. What
happens instead is that I seem to not type anything. When I select the other
tab, I find out that what I was typing was entered into the autofocusing
textfield. Even hitting the enter key is registered.

II. When typing into a textfield
1. On an existing tab with a textfield
2. Open another tab, go to a site with an autofocusing textfield
3. Before it loads, go back to the previous tab. Focus the textfield and start
typing

Again, I seem to type nothing. And, again, when I go to the other tab I find
that this other textfield had received focus, and whatever I typed was
registered here instead.”