User Agent: Mozilla/5.0 (Windows NT 5.0; rv:5.0) Gecko/20100101 Firefox/5.0 Build ID: 20110615151330 Steps to reproduce: changed (widened) domain using document.domain from within an IFRAME whose src was a data-url Actual results: i found that not only iframe document.domain changed but also iframe's parent document.domain was changed. Using same code from within an Iframe whose src is http url does work as expected (change document.domain of iframe only) Opera works correctly both with data-url and http url. Safari/Chrome do not let you change document.domain when using data-url, works fine with http url Expected results: only iframe's document.domain should change

The iframe and the parent document have the same security origin (object identity, note!); setting document.domain changes that one shared security origin. So the behavior is expected given the current security model for data: URLs in Gecko: they just count as part of the page that loaded them for security purposes. I'm not sure that's necessarily a sane model, but no one has proposed a sane alternative either...

Pretty sure this is no longer the case due to bug 1324406.