I have been having the same issue but when I looked at /wp-content/plugins/index.php i see a lot of random code and it ends like this:
<?php
// Silence is golden.
?>
I googled that string and it turns out that’s a hack, it even has it’s own plugin to prevent it. I haven’t found a fix for this other than renaming your old plugin files and re-installing them but since this is the 2nd time this has happened to me, I’m going to take some extra precautions.
