Many high-profile browser toolbars released over the years have been fraught with problems, either intentionally as malware or injected with computer viruses or due to poor or conflicting programming when considering multiple toolbars being included on the single browser.
During the 2000s, there was a proliferation of browser add-ons produced and released by a variety of software companies, both large and small, which were designed to extend the browsing experience for the end user.
Due to this popularity, and the ease with which users could have these installed, there was additionally an adoption by malware, adware, and other privacy-invasive tracking tools.
[1][2] Many unscrupulous companies use software bundling to force users downloading one program to also install a browser toolbar, some of which invade the user's privacy by tracking their web history and search history online.
[19] In Opera 11 or later,[20] toolbars can be created as extensions[21] that add buttons[22] to the browser window.
Some toolbar developers use a different approach and make the browser extension inject a JavaScript file in every web page visited by the user.
[33][34][35] This process varies by browser type, version, OS, and toolbar provider.