WordPress Version: 4.7
/**
* Checks that a JSONP callback is a valid JavaScript callback.
*
* Only allows alphanumeric characters and the dot character in callback
* function names. This helps to mitigate XSS attacks caused by directly
* outputting user input.
*
* @since 4.6.0
*
* @param string $callback Supplied JSONP callback function.
* @return bool True if valid callback, otherwise false.
*/
function wp_check_jsonp_callback($callback)
{
if (!is_string($callback)) {
return false;
}
preg_replace('/[^\w\.]/', '', $callback, -1, $illegal_char_count);
return 0 === $illegal_char_count;
}