Enable strict validation of required fields Create a form with required text field and without client validation (for example, hack moodleform_mod.php and remove 'client' from line $mform->addRule('introeditor', get_string('required'), 'required', null, 'client'); ) Enter spaces, newlines. Try entering several spaces and then newline (TinyMCE treats it specially) Submit form, make sure validation fails Enter cyrillic text Submit form, make sure there are no errors Check in Atto and TinyMCE