SmashTab is the extension that changes default search engine and bookmarks on the browser without permission

From 2-spyware.com

SmashTab

SmashTab – the toolbar that is considered a browser hijacker because it affects every online search by delivering sponsored content on the list. The application can be promoted as a great tool, useful addition to your web browser, but it manipulates settings, so every browsing session turns into redirections with commercial content and sponsored pop-ups. If you install this Toolbar yourself, you agree with those changes and other alterations that the program can make automatically. It is possible to fall for the false claims and add the extensions on purpose, but the main way to spread this intruder is software bundling. 

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