SlowMist: GebProxyActions contract access control vulnerability led to the theft of 5.9436 ETH

According to SlowMist's monitoring, the GebProxyActions contract suffered a loss of approximately 5.9436 ETH due to a lack of caller access control. Affected users previously called GebProxyActions.quitSystem directly instead of through a DSProxy delegated call, resulting in ownsSAFE[safe] being set to the GebProxyActions contract.

The attacker directly called GebProxyActions.quitSystem(manager, safe, dst), bypassing the safeAllowed check of GebSafeManager and transferring the collateral to themselves.