core files changed

Hello,
I recently got critical errors (high severity issues) by Wordfence about some WP core files changing. These files are

• wp-login.php,
• wp-signup.php,
• wp-comments-post.php,
• wp-load,
• wp-activate.php and
• license.txt.

That what I see, when I go trough Details->View Difference for any of these files, seems to me not to be malicious changes but surely wasn’t by me.
I maintain two wordpress websites (dev and production) on different VPS with WP 5.6.8 and Woo 4.7. These critical errors appeared on the developer server only. May I have an advice on this matter, please?
Thank you in advance.