Two security issues and some vulnerabilities have been discovered in PHP-Calendar, which can be exploited by malicious people to disclose sensitive information and conduct cross-site scripting, and cross-site request forgery attacks.

1 )The "update08.php" and "update10.php" scripts are stored with insecure permissions inside the web root. This can be exploited to gain knowledge of sensitive information (e.g. database host, user name, password, name, table prefix, and type) by requesting the files directly.

2) Input passed to the "lastaction" parameter in index.php (when "action" is set to "login") is not 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 an affected site.

3) Input passed via the "sort" and "order" parameters to index.php (when "action" is set to "search") is not 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 an affected site.

4) The application allows users to perform certain actions via HTTP requests without performing any validity checks to verify the requests. This can be exploited to e.g. add an administrative user or create a calendar event by tricking a logged in administrator into visiting a malicious web site.

The security issues and the vulnerabilities are confirmed in version 1.1. Other versions may also be affected.

Solution
Delete the update scripts after successfully updating the system and edit the source code to ensure that input is properly sanitised. Reportedly, vulnerability #2 is fixed in version 2.0 Beta7. Vulnerabilities #3 and #4 are fixed in version 2.0 Beta8.

Provided and/or discovered by
1) Justin C. Klein Keane
2) The vendor credits Vupen.
3, 4) The vendor credits Teemu Vesala, Qentinel and Skipfish.

Changelog
Further details available to Secunia VIM customers

Original Advisory
PHP-Calendar:
http://php-calendar.blogspot.com/2010/05/php-calendar-20-beta7.html
http://php-calendar.blogspot.com/2010/06/php-calendar-20-beta8-is-out.html

Deep Links
Links available to Secunia VIM customers