They also added some new JavaScript in their pages which I casually saw while searching in the html for the worm payload.
The code was the following :
//<![CDATA[
(function(g){var a=location.href.split("#!")[1];if(a){g.location=g.HBR=a;}})(window);
//]]>
Do you spot the issue?
It search for "#!" in the Url and assign the content after that to the window.location object. And it is present in (almost?) every page on twitter.com main site.
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