Some time ago I was surprised that my Google Search page was replaced by something else after I returned from some spammy page (opened in another tab).<p>As the browser I use, Opera 12, also treats all links manually opened in the new tab as if they had target=&quot;_blank&quot;, giving them opener access, I decided to remove the window.opener altogether by replacing the &quot;opener&quot; string with &quot;opera&quot; in the opera.dll. This way it gets overwritten by the normal window.opera variable and is essentially hidden. So far I haven&#x27;t encountered a site legitimately relying on this behavior.