Susam Pal has reported a vulnerability in Community Architect Guestbook, which can be exploited by malicious people to conduct script insertion attacks.

Some input passed to "cgi-bin/guest" when signing the guestbook isn't properly sanitised before being used. This can be exploited to inject arbitrary HTML and script code, which will be executed in a user's browser session in context of an affected site when the malicious user data is viewed via "fsguestbook.html".

Solution
Edit the source code to ensure that input is properly sanitised.

Provided and/or discovered by
Susam Pal

Changelog
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