guestbook.pl cleanses user-inserted SSI commands by removing text between "<!--" and "-->" separators, which allows remote attackers to execute arbitrary commands when guestbook.pl is run on Apache 1.3.9 and possibly other versions, since Apache allows other closing sequences besides "-->".

Cross-site scripting (XSS) vulnerability in Matt Wright Guestbook 2.3.1 allows remote attackers to execute arbitrary web script or HTML via the (1) Your Name, (2) E-Mail, or (3) Comments fields when posting a message.

Cross-site scripting (XSS) vulnerability in Matt Wright Guestbook 2.3.1 allows remote attackers to execute arbitrary web script or HTML via the (1) url, (2) city, (3) state, or (4) country parameters. NOTE: the provenance of this information is unknown; the details are obtained solely from third party information, although it is likely that they are the result of post-disclosure analysis.