Hypotetical: Assuming a cloud provider gets FULLY malicious, could they steal keys from LN node running on it? Or are keys separated/secure and all damage cloud provider could do is shut it down in which case LN operator can recover backups on new server and be operational again? Put your adversarial hats on.
If the machine is virtualized, such as is commonly called a VPS or Droplet, then yes it's possible for the hosting company (rogue employee, hack or "hack") to exfiltrate keys of all kinds. It is for this reason, I would recommend only a bare-metal install with full-disk encryption for hosting any of these things with real money, say more than a 0.01 BTC.
If you want to go higher security you would prepare the machine while in your possession and then send it for colocation. Higher still is to keep it under your or your company's physical control.
In general the lengths you go for security have to depend on your threat model and the value of what's being protected.
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Yes. It has happened before with medium_of_exchange node.
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Yes, I remember it
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