The Joomla team have released Joomla 2.5.2 and associated patch files. It is highly recommended that you upgrade all Joomla 2.5x websites as this patch includes a high severity security fix to protect against core SQL injection.
details here
http://developer.joomla.org/security/news/391-20120301-core-sql-injection
and here
http://developer.joomla.org/security/news/392-20120302-core-xss-vulnerability
Announcement here:
http://www.joomla.org/announcements/release-news/5415-joomla-252-released.html