Joxean Koret has reported some vulnerabilities in WebCalendar, which can be exploited by malicious people to conduct cross-site scripting attacks, disclose system and sensitive information, and bypass certain security restrictions.

1) Input passed to some parameters in various scripts isn't properly sanitised before being returned to the user. This can be exploited to execute arbitrary HTML and script code in a user's browser session in context of a vulnerable site.

Examples:
http://[victim]/view_entry.php?id=41972"[code]&date=20041001
http://[victim]/view_d.php?id=657"[code]&date=20041009
http://[victim]/usersel.php?form=[code]&listid=20&users=demo,demo1,demo2
http://[victim]/datesel.php?form=[code]&fday=rpt_day&fmonth=rpt_month&fyear=rpt_year&date=20041001
http://[victim]/datesel.php?form=editentryform&fday=rpt_day"%20[code]&fmonth=rpt_month&fyear=rpt_year&date=20041001
http://[victim]/includes/trailer.php?user=[code]
http://[victim]/includes/styles.php?FONTS=[code]

2) Input passed to the "return_path" parameter in "login.php" can be exploited to inject malicious characters into HTTP headers. This may allow execution of arbitrary HTML and script code in a user's browser session in context of an affected site.

This can also be exploited to perform web cache poisoning.

3) Input passed to the "user_inc" parameter in "init.php" isn't properly verified, before it is used to include files. This can be exploited to include arbitrary files from local resources.

4) Some internal variables in "view_entry.php" and "upcoming.php" can be overwritten by external parameters. This can be exploited to bypass certain security restrictions.

It is reportedly also possible to disclose the full path to "validate.php" by accessing it with an empty "encoded_login" parameter.

Solution
The vulnerabilities have reportedly been fixed in the CVS repository.

Provided and/or discovered by
Joxean Koret

Changelog
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