http://www.easyphpcalendar.com/forums/showthread.php?p=45554#post45554

technical details are not issued however the two issues are pertaining to
XSS in following two files in the package.

index.php
datePicker.php

This issue affect both free version i.e. version 6.
as well as commerical version < 7.0.13

Changelog visible here for v7 :
http://docs7.easyphpcalendar.com/source/ChangeLog/changeLog.htm
for v6 patch is listed here :http://www.easyphpcalendar.com/v6download.php
 as  Security Patch - Released April 9,
2013<http://www.easyphpcalendar.com/files/EPC6Patch.zip>

Thanks in advance.

-Anant