Zone Labs IMsecure Active Link Filter Bypass

[Kurczaba Associates advisories <advisories@xxxxxxxxxxxx>]

Zone Labs IMsecure Active Link Filter Bypass
http://www.kurczaba.com/html/security/0410141.htm
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Overview:
A vulnerability has been discovered in the Zone Labs IMsecure Active Link Filter

Vendor:
Zone Labs (http://www.zonelabs.com)

Affected Systems/Configuration:
Versions of IMsecure and IMsecure Pro prior to 1.5

Vulnerability/Exploit:
The Active Link filter blocks potentially dangerous URLs in IM messages.
For example, IMsecure will remove URLs with extensions of .vbs, and .exe. By 
using hex encoded characters in the file extension of the URL, it is possible 
to bypass the Active Link filter.

Workaround:
Upgrade to version 1.5 or higher

Proof of Concept:
http://www.example.com/somefile.e%78e

In the example above, "78" is hex for "x".In plain English, the URL reads:

http://www.example.com/somefile.exe

Date Discovered:
April 1, 2004

Fix Available:
October 12, 2004

Severity:
Low

Credit:
Paul Kurczaba
Kurczaba Associates