An unknown version of wordpress (4.1.8) ?

Hello there,
This morning was a normal day, with the usual updates.

Checking WP versions of all my sites (I wrote a small bash script that does this for me), I was surprised to discover some WP 4.1.8 ...

I have checked three times before coming to ask here ...
4.1.8 No, nowhere ... https://codex.wordpress.org/WordPress_Versions

And yet:

#cat wp-includes/version.php
<?php
/**
 * The WordPress version string
 *
 * @global string $wp_version
 */
$wp_version = '4.1.8';
...

I have more than a dozen sites like that.
You would have an idea of what is happening with my WP?

Thank you.
Laurent.