Recaptcha plugin does not appear in login/register when using internet explorer 11 or edge. Works for all other browsers.
This should only be an warning, that you should test captcha with ie11/edge if you're using it.
Happen with joomla 3.5.(0/1)
Link:
https://issues.joomla.org/tracker/joomla-cms/9623
Last change: 07.05.2016 11:41