Submitted by HE1M
In the contract GovNFT, it is possible to bridge the governance NFT to other chains. It is also stated in the document that:
It is assumed that there is only one unique NFT per token id. But there is a scenario that can lead to more than one NFT with the same token id on different chains.
https://github.com/code-423n4/2022-12-tigris/blob/588c84b7bb354d20cbca6034544c4faa46e6a80e/contracts/GovNFT.sol#L124
https://github.com/code-423n4/2022-12-tigris/blob/588c84b7bb354d20cbca6034544c4faa46e6a80e/contracts/GovNFT.sol#L168
https://github.com/code-423n4/2022-12-tigris/blob/588c84b7bb354d20cbca6034544c4faa46e6a80e/contracts/GovNFT.sol#L178
lzReceive ==> nonblockingLzReceive ==> _nonblockingLzReceive ==> _bridgeMint
https://github.com/code-423n4/2022-12-tigris/blob/588c84b7bb354d20cbca6034544c4faa46e6a80e/contracts/GovNFT.sol#L206
retryMessage ==> _nonblockingLzReceive ==> _bridgeMint
The vulnerability is that when the message is failed, it is not considered as consumed, so in case of a failure in endpoint it is possible to have failed messages and be able to mint it at the same time.
Please note that if this scenario happens again, more NFTs with the same token id X will be minted to Bob on different chains.
It is recommended to track the consumed messages, and add a consumed flag whenever the function lzReceive is called, because it will either immediately mint the NFT or add it to the failed messages to be minted later.
GainsGoblin (Tigris Trade) confirmed 
Alex the Entreprenerd (judge) commented:
GainsGoblin (Tigris Trade) resolved:
