Chinese security researchers have admitted that they inadvertently released code that might be misused to exploit an unpatched Internet Explorer 7 vulnerability.
Scripts to pull off the trick were already on sale in underground forums before the inadvertent release. Even so, anything that increases the likelihood of digital delinquents getting their hands on the exploit is unwelcome.
VeriSign's iDefense security division reports that attack code was up for sale at prices of up to $15,000 through underground forums. Prices are likely to slide following the escape of assault code from labs run by KnownSec.
Security tools firm eEye reckons the flaw has been the target of exploitation since 15 November.
According to iDefense, KnownSec made the code available after failing to realise that last Tuesday's Microsoft bulletins failed to fix the underlying vulnerability behind the bug, which revolves around IE7's handling of malformed XML tags. A explanation of what happened by KnownSec (in Mandarin) can be found here.
The flaw affects XP and Vista users, and creates a means to load Trojans or other forms of malware onto even fully patched Windows boxes simply by tricking surfers into visiting maliciously constructed websites. Thus far the attack method has been restricted to delivering game password stealers, the Internet Storm Centre reports.
Microsoft is investigating reports of attacks and considering its options. The timing of the attack in the run up to the holiday period and just after a bumper batch of eight bulletins suggests an out of sequence patch might be on order before the next scheduled Patch Tuesday, on 13 January. ®