After disable all plugin the problem is gone, and the suspect is from the one of the plugin.
And after search with this query :
SELECT title, phpcode, hookname, product FROM plugin WHERE phpcode LIKE '%base64%' OR phpcode LIKE '%exec%' OR phpcode LIKE '%system%' OR phpcode like '%pass_thru%' OR phpcode like '%iframe%';
The code above from :
http://www.vbulletin.com/forum/forum...37#post3506437
I got the result like this :
--------------- Added [DATE]1381973259[/DATE] at [TIME]1381973259[/TIME] ---------------
how to solve that?can I only delete the database record that shown above?