Shouldn't be necessary Rated 5 out of 5 stars
Yes, it's there by design, But it's absolutely stupid. For one, you have to be really stupid to fall for the attack, For another, there's another less intrusive way to fix it: require two actions on different places on the screen.
And what's really annoying is that, for any site other than addons.firefox.org (which is safe), Firefox already does this with you having to allow the site to download content.
So, it's a completely pointless feature that keeps being thrusted upon us because people won't use their brain.
And that's not even covering the ability for other solutions. It's not like any other browser does this.