Submitted by MrPotatoMagic
https://github.com/open-dollar/od-contracts/blob/f4f0246bb26277249c1d5afe6201d4d9096e52e6/src/contracts/proxies/ODSafeManager.sol#L136 
https://github.com/open-dollar/od-contracts/blob/f4f0246bb26277249c1d5afe6201d4d9096e52e6/src/contracts/proxies/ODSafeManager.sol#L41
A safe is associated with a unique safeHandler. This safeHandler can give permissions to addresses through the allowHandler() function which stores these approvals/disapprovals in the handlerCan mapping. Now lets say there is a safeHandler which has permissioned some addresses in the handlerCan mapping. When this safe is transferred to a new owner, the previous permissions that were added to the safeHandler are still attached to it without the new owner realizing it.
Here is the whole process:
https://github.com/open-dollar/od-contracts/blob/f4f0246bb26277249c1d5afe6201d4d9096e52e6/src/contracts/proxies/ODSafeManager.sol#L112C1-L115C4
It is not possible to remove the handlerCan permissions in the transferSAFEOwnership() function since it is stored in a mapping. The only solution to this would be to add another key field (named _owner) to update the safeHandler permissions correctly whenever a safe is transferred. We can see this pattern implemented for the safeCan mapping, which correctly updates the safe permissions on transfer.
Solution (use this mapping instead):
MiloTruck (Judge) decreased severity to Medium and commented:
