I had the same (?) issue last night. Popups over and over again but it wasn't related to any one website. I did not have the Play Store open at the time and it seemed to recur when I did a search from the search bar. It happened in Chrome, Firefox, and Safari.
I deleted Firefox and Chrome as well as related files in Application Support. The popups stopped in Chrome and Firefox but continued in Safari for a while. They all stopped at a seemingly random time when I was away from the computer for a moment.
After reinstalling Firefox, I get this error. I do not get this in Chrome or Safari. I'm not sure if they are less secure or if the Web Shield isn't running in those any longer or what.
Here are the details.
I downloaded MalwareBytes Anti-Malware and the scan came up clean. I followed all of the steps that applied to me on this page. The only thing I didn't do is try a new network since that wasn't practical last night. Now the popups have stopped so I don't know if that would tell me anything.
https://support.malwarebytes.com/customer/portal/articles/2045704-what-should-i-do-if-malwarebytes-anti-malware-for-mac-didn-t-solve-my-problem-?b_id=9511I ran a scan on Avast, which found two infections in old install files. I deleted those but the popups stopped before I deleted these files.
I also scanned the network, which appears OK and my roommate doesn't seem to be having a problem.
I searched for "blacklisted url blocking (URL:Mal)" but I don't think that quite applies (but I could be wrong -- I'm not a security expert). So now my questions are:
1) How do I make Firefox usable?
2) Am I safe using Safari and Chrome in the meantime?
3) What the hell happened last night and are there further steps I need to take to make sure I am safe?