php - Component K2 is damaged, says class K2HelperHTML not found -

my joomla powered website hacked several days ago, after cleaned , restored, problem emerged.

on back-end, when click components -> k2 , fatal error appears:

fatal error: class 'k2helperhtml' not found in ~/administrator/components/com_k2/k2.php on line 77 

i compare k2.php file working site's k2.php no differenced found.

then inpsected file class k2helperhtml defined, believe ~\administrator\components\com_k2\helpers\html.php, doesn't show differenct working site's corresponding file.

now i'm stuck here, should next repair this.

have tried reinstalling recent version? place start. use joomla installer install latest version.