How do I get rid of a Install Flash Player pop-up in Android?

[AC Question]

Install Flash Player pop-up in Android

When I try to open Google/Yahoo pages on all browsers on my Android mobile phone, I see an Install Flash Player pop-up which doesn't go away even after factory reset. I'm able to access other websites though. How do I get rid of it? I scanned my phone using Malwarebytes Anti-Malware and it didn't detect any virus.