Firefox has a decent enough popup blocker built-in, but like most blockers it doesn’t stop Flash popups. To fix this do the following:
- Type about:config into the Firefox address bar.
- Right-click on the page and select New and then Integer.
- Name it privacy.popups.disable_from_plugins
- Set the value to 2
The possible values are:
- 0: Allow all popups from plugins.
- 1: Allow popups, but limit them to
- 2: Block popups from plugins.
- 3: Block popups from plugins, even on whitelisted sites