This is a very lightweight addon that uses the standard Firefox popup blocker and will respect its whitelist (it just changes a single setting).
When the addon is enabled, all popups will be blocked - even user initiated ones. When the addon is disabled (red cross on toolbar icon), the Firefox popup blocker works as standard.
Acknowledgements:
Icon by Deivid Sรกenz from the Noun Project (CC BY 3.0)
