Includes file class_http.php being truncated

This is the strangest thing I have ever seen —

Alright — I need serious help and expertise here —-
This has happened three times so far today —–

the class-http.php file in the includes directory has been truncated somehow —

the original file has 1955 lines —

earlier today — I started getting the syntax area — and I tracked it down — and that file only had 588 lines in it — the last line was an if statement with nothing after it —

I replaced it with the original — everything was fine

then this afternoon — it happened again — and there were only 467 lines in the file — I replaced it with the original — everything was fine

then it just happened again — now the file only has 1157 lines in the file — Once I put the file back — everything works again —

How could this be happening — What is that file used for — it looks like it handles cookies and stuff —-

I have no idea what to do — to even start looking for the issue HELP HELP