Firefox 3.5 issue

Apparently, there's a new "feature" in Firefox where if you click and hold on a tab, then drag the mouse down into the page and release, the tab will close in the current window and open in a completely new window. I don't think I like this new feature very much. I've done this several times on accident, thinking it was just a crazy random bug. From what I can tell, at least in the five minutes that I've looked for a solution so far, there's no way to disable this functionality aside from using an addon, which I'm not quite that desperate to use, at least now that I know that it's not an actual bug and is supposedly intended behavior. I can click and drag the tab back into the original window which closes the newly created window, so it's not a complete loss. It's just that it's too easy to trigger this new crap unintentionally and it's somewhat annoying, but now that I know about it, I could possibly see some actual use for it someday.

After experimenting with it a bit, it appears that it depends upon where the mouse is when you release it that determines the behavior. If you're just over a none editable part of a page, then it does the above. However, if you're over an editable text field, it does not do the above, and instead merely pastes the url for the tab into the text field.