For the last week or so, I've been getting these popup ads for Builder's Warehouse whenever I open Firefox (see screenshot attached). However, - the ads aren't "in the browser" window they're right at the top of my screen - There's no options I can find to see any information about where the ad comes from - The ad usually disappears quite fast, preventing me from investigating further I don't imagine it could be being shown by Google because it appears without me opening Google. So it kind of seems like it's probably being done by the browser. But I also struggle to believe that Firefox would be purposefully showing me such invasive advertising. So I'm guessing it's malware. But I don't know. Please help me to understand: - Where does this ad come from? - If it's malware, any ideas how to get rid of it? - If it's Firefox, and they're being shown because of a mistake on my part, how do I turn them off?

Thanks