Mac Clean Pop Up
MacBook Air, OS X Yosemite (10.10.4), MacBook Air3,2
remove the plugin
then shut down Safari and open it again holding down the SHIFT key
If the issues persists then for futher analysis you may post an Etrecheck report.
and/or you can check your system for Malware using malwarebytes for Mac. Etrecheck looks for malware as well.
if you have any questions about the legitimacy of these products do not hesitate to ask around.
Popup remover – Scam Zapper
If the pop-up reloads, force quit Safari (command - option/alt - esc) and reopen with the shift key held down. If that doesn't work, disconnect from the Internet, go to Safari/History and delete the website. Quit and reopen with the shift key held down. Then reconnect to the Internet.
Thank you!!
Mac Clean Pop Up