I have a file called Core that is about 10 Mb. It is in the same directory that all the other main files of my website are in, such as Index.php. When I open it up, it looks encrypted. Can anyone tell me what the purpose of this file is?
My main concern is if the developer I worked with created this file for malicious purposes if he decides to use it. Is that possible?
Quite probably this is what's called a core dump file. There is nothing malicious about it. It is used for debugging, and is safe to delete.
Of course, I have no way to know for certain without any additional information, but I'd bet it's a core dump file.