Şimdi duyuru yapıldı. Wordpress'in de benzer bir güncellemesi olmuştu.

After releasing Joomla! 1.5 stable we have discovered a high priority security issue. The vulnerability has been discovered in XML-RPC in combination with the blogger API. There is a security problem in this code that makes it possible to alter the articles on your site (including removal).

Joomla! 1.5.1 features

• Fixed XML-RPC/Blogger security issue.
• Fix to sef issues including creation of optional livesite parameter if
  needed which will also allow reverse proxy.
• Change to mass mail so that blind carbon is used, protecting email addresses
  of your users.
• Fix to date function that was causing an error in the end publication date
  for some systems.
• Fixed UTF 8 database detection
• Addressed a number of internationalization issues.
• Fixes to a number of minor issues