Profile: Akhil

add_filter( 'cred_form_validate', 'tssupp_validation', 10, 2 );
function tssupp_validation( $error_fields, $form_data ) {
 
    // split error_fields into fields and errors
    list( $fields,$errors ) = $error_fields;
 
    // apply to specific form
    if ( $form_data['id'] == 6590 ) { 
 
        // disallow restricted names
        $restricted = array( 'admin', 'administrator', 'author' );
 
        if ( isset( $fields['user_login']['value'] ) && in_array( $fields['user_login']['value'], $restricted ) ) {
 
            //set error message for my_field
            $errors['user_login'] = 'That username is restricted, please try another';
        }
          
    }
 
    return array( $fields, $errors );
}