[amilz]

• Adds fetchProgramUpgradeAuthority, which reports who can replace a program's code: the same data solana program show prints under Authority and Last Deployed In Slot.
• Loader v2 programs are reported as immutable. For loader v3 programs it returns the program data account's authority and deploy slot, plus authorityKind: keypair (on-curve), pda (off-curve, e.g. a multisig vault), or none.
• Throws on missing, non-executable or non-v2/v3 accounts, the same way getProgramAuthority does.

const result = await fetchProgramUpgradeAuthority(rpc, programId);
// { loader: 'v3', authority, authorityKind: 'keypair' | 'pda' | 'none', lastDeployedSlot, program, programData }
// { loader: 'v2', authority: null, authorityKind: 'none', program }

Got the idea from @robre post

How to check who can change the code of a Solana program you use. Takes 30 seconds:

1. Find the program ID (docs, explorer, or the transaction your wallet asks you to sign)
2. Run: solana program show <PROGRAM_ID>
3. Look at the Authority line

• none: immutable. Nobody can change the code.
• a normal wallet: one key can replace the program with anything. That key is the whole security model.
• a Squads multisig vault: check the members, the threshold, and whether there's a timelock.

Also look at Last Deployed In Slot. Recent upgrades you didn't hear about? Ask why.

Drift in April was a reminder that admin keys get compromised. If one key can change the program holding your money, that's your risk too.

CC @Woody4618