Georgi Guninski security advisory #8, 2000

IE 5.x allows executing arbitrary programs using .chm files

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There is a vulnerability in IE 5.x for Win95/WinNT (probably others) which allows executing arbitrary programs using .chm files. Microsoft Networking must be installed.

The problem is the window.showHelp() method which opens .chm files. IE disallows opening .chm files with the http protocol, but allows opening if the .chm file resides on MS networking server or a local drive.
In this case the .chm file is opened even if it is on a remote host. In turn .chm files may execute arbitrary programs using the "shortcut" command.

Demonstration which starts Wordpad

Workaround: Disable Active Scripting.

Copyright Georgi Guninski

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