About rel=noopener
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="_blank", giving them opener access, I decided to remove the window.opener altogether by replacing the "opener" string with "opera" in the opera.dll. This way it gets overwritten by the normal window.opera variable and is essentially hidden. So far I haven't encountered a site legitimately relying on this behavior.