I would strongly recommend changing hosting providers based on the above information. It sounds like there are some major configuration issues with the server.
..and I think this very well might happen. Our client had to show his CEO a report as to why this has happened. I have a feeling that they're going to want a drastic change for their own sense of security.
The only explanation I can give would be a change to the server php.ini file. I don't have enough information to give a definitive answer regarding the cause, but normal cPanel updates would be unlikely to cause the problem.
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