I had noticed of late that popups seemed to be coming through my Firefox popup blocker with some frequency. I was a little perplexed but didn’t give it much thought (it wasn’t that frequently). The other day, Asa posted something about it. Basically, rather than using javascript embedded in HTML, the guys who get through the popup blocker are using plugins (such as Flash) to open windows. Luckily, Firefox offers a way to stop these, but it’s turned off by default because turning it on blocks potentially valid functionality within the plugins. I’ve turned the option on, though, and here’s how (screen scraped from Asa’s blog):

To block pop-ups from plugins, open your Firefox 1.0 or 1.0.1 browser, type about:config in the address field. Right-click in the resulting config page somewhere and select New -> Interger. Type privacy.popups.disable_from_plugins in the resulting dialog, hit OK, type 2 in the next dialog and you’re all set.

This pref can actually take three values:

• 0: open allowed
• 1: the opened windows are treated as popups, but they’re allowed to open (we limit the number of these types of popups)
• 2: the window is a popup, block it

In the image accompanying this entry, the preference is highlighted. This is the view you get when you enter “about:config” in the Firefox address bar (though yours won’t have the preference I’ve highlighted until you’ve added it). To add the preference, just right click anywhere in this screen and follow Asa’s instructions. So far, it’s worked great for me, and with no ill side effects.