Viewer Extension Browser Hijacker

"Viewer" is the name of a browser extension that will claim it has useful functionality, while in reality it works as a browser hijacker.

Browser hijackers are usually categorized as potentially unwanted software, also known as PUPs or potentially unwanted programs. PUPs occupy the middle ground between legitimate software and fully-featured, more dangerous malware.

Browser hijackers may make a number of changes to your browser of choice. Those changes include swapping out your home page to a different one, changing the default contents of new tabs and changing the default search engine used by the browser.

Additionally, some hijackers have functionality that allows them to either inject ads into pages you browse or display them as pop-ups. Some browser hijackers can also track your browsing activity and store information about your search queries. This information is of value to advertising companies and ad networks and can be re-sold to them without your consent.

All of this makes the presence of any browser hijacker on your system undesirable, no matter if it is the "Viewer" extension or some other variation.