Hello again, Microsoft Internet Explorer seems to have a soft spot for browser entrapment vulnerabilities. Just to recap, in these attacks, the user is made believe he had left a webpage (and the URL bar or SSL state data reinforce him in this belief) - but in reality, is prevented from doing so, and his browser continues to display assorted content originating from the attacker. This is a close, but somewhat more sinister relative of vanilla URL bar spoofing. I reported a few of each kind in the recent months. Well, here's another one, this time based on document.open() calls. In essence, repeatedly calling this function after a new URL is entered by the user, before onBeforeUnload is invoked, inhibits page transition - but target URL bar state is retained. This is remarkably silly. A live demo is available here: http://lcamtuf.coredump.cx/ietrap3/ That is all. ... PS. The promised tidbit - since I'm leaving for a while and won't have time to research this - in Firefox, javascript: windows can set 'domainless' cookies by specifying 'domain=.' - for example: open("javascript:document.cookie='foo=bar;domain=.'","_blank"); Fortunately/unfortunately, these cookies do not get sent to all sites - no session fixation - though can be retrieved by other null-domain javascript: / data: pages. Specifying other domains won't work. Multiple periods will be trimmed. Path can be set arbitrarily, with certain exceptions. Null-domain cookies load properly when stored in cookies.txt. Q: can this be used in a manner more sinister than merely facilitating exchange of "markers" between various user-tracking sites? /mz