Forbid or validate certain words in my custom fields
Hello! My problem's as follows:
My website uses ClassiPress to allow registered users post ads through a form with custom fields. But the trouble is that a particular user has been promoting his own page and posting spam.
What I need is forbid or validate certain words in that custom fields like: post title or description. (and words like: "mypage.com - the world's best website"). This, using validation or some other method.
Below I attached a picture showing my form on the page, its source code and php files related.Solve this problem is very urgent for me please! if you help me I will be immensely grateful.