It's not the first time that I saw some popups opened when surfing with my
Firefox, but today the limit o my patience was reached...
I was surfing on ActiveWin.com but when I've
reached the site, 2 popups was opened (they are opened only the first time you
visit the site). 
Firefox popup blocker is now bypassed? Seems that the answer is yes: sites
that uses plugins (like Flash for example) now are able to open popups in
Firefox (they use the plugin to launch it). Searching on Google for this
problem, I've found a post
on a forum that seems working good (obviously, I can't disable the Flash
plugin).
The solution (from the post) is this:
- Open Firefox.
- Type about:config in the address bar, and
press enter.
- Right-click in the resulting config page somewhere and select New ->
Integer.
- Type "privacy.popups.disable_from_plugins" in the resulting dialog
and press OK.
- Type "2" on the value dialog and click OK. You're ready...
The values admitted are these:
- 0 = all window opens are allowed
- 1 = opened windows are treated as popups, but they're allowed to open
anyway (with limitations on the popup window number)
- 2 = windows are not allowed to open popups
If you don't want to modify a Firefox settings, there's also another road I
think... these types of Popups (as I've written before) comes for the main part
from Flash pages or banners, so you can install the FlashBlock extension for
Firefox that replaces all the Flash contents with a
placeholder on the page that allows you to click to view the content.
If you're on a trusted site, you can choose to play the Flash
movies...