After installing the latest downloads plugin a message appears in the error log:
Sat Jan 12 19:22:57 2019 - 184.108.40.206 - E_WARNING(2) - Use of undefined constant ext - assumed 'ext' (this will throw an Error in a future version of PHP) @ .../plugins/downloads/include/functions.php line 415
$len = strlen(ext);
$modurl = substr($url, 0, -$len) . $ext;
I do assume it's a typo.
Yes, I'm on php 7.2