ReCaptcha v2 plugin for Joomla 2.5

Google support for Captcha v1 ends on 31st March 2018, but the Joomla 2.5 Recapthca plugin stopped working yet.

To keep it working and upgrade it to Captcha v2, here there is a fix for the captcha plugin shipped with Joomla 2.5:

Download and expand the fix: recaptcha.php.zip
On your site, backup and open the file ./plugin/captcha/recaptcha/recaptcha.php
Replace its content with the content from the (expanded) fix
Everything else, including admin UI, remains unchanged.
Thats’s it, just reload the page — also cache deletion shouldn’t be necessary.