Is it true, that Arbitrums L1 smart contacts are upgradeable and thus a risk?

https://l2beat.com/scaling/projects/arbitrum

Please correct me if I'm wrong. I'm trying to assess the risk at Arbitrum. Do I understand it correctly, that the smart contracts forming the L2 can be upgraded by the security council at any time without delay? Doesn't that mean, that Arbitrum could in theory maliciously upgrade the contract and erase people's funds on L2?

Even if that happens, couldn't we then legally do something about it - or in the worst case create a copy L2 with the last state before the "hack" where people can get their funds out of the frozen copied L2?

Edit: I realise there is one problem with creating a social consensus copy of the L2 and refunding the people their funds. Namely, that the L2 tokens are always backed by their L1 tokens in the smart contract for the original L2. If Arbitrum makes a malicious upgrade AND makes the contract unupgradeable, then the funds are lost and people on the socially recovered L2 couldn't actually redeem their L2 tokens for L1 tokens. That would e a disaster.

What do you think?

Please forgive me, if the question is noob ????