The problems that have been mentioned on this thread can be caused by a number of things, the most likely thing is MALWARE, a lot of Virus Protection Software does not protect you from MALWARE, currently Apple Users on all devices, iPhone, iPad and Mac.
Flashback Malware, I use a Mac and details are in the link below from the company I use for Virus Protection. It is not connected with ShoppingTelly.com in anyway and could occur on any link you may click.
https://www.intego.com/mac-security-...ith-scareware/
..... and this is a link from the Apple Website
https://support.apple.com/en-gb/HT202458 it can affect any Apple Device.
That is the main one that is causing issues at the moment, but even if you are not using an apple device you can still get infected with MALWARE.