What is the index.html.bak.bak file in the modx folders?

Question

MODX

In two folders core/docs and core/lexicon I found files with this name.

Answer 1

urgently check and clean malicious code ( https://revisium.com/ai/ ).
modx update to the latest version.

Answer 2

We used to add index.html to prevent directory listing. Recently there was an epidemic on Modx, maybe from there. In some cases index.php was added with malicious code.