Note: this finding was originally submitted separately by the warden at a higher severity; however, it was downgraded to low severity and considered by the judge in scoring. It is being included here for completeness.
Allowing to modify the delay period without minimum threshold can result in set the delay period to a too short period or even zero ,which is allowed according to the code , and this could lead to allowing a malicious ScheduleUpgrade message to pass and a malicious account can gain control over all the contracts of the protocols. 
In the Root.sol contract, the protocol implements a maximum threshold in the function file() which can modify the delay variable, so the possibility of the set the delay period to a very long period exists and also setting the delay period to a very short period is still possible, as shown in the file() which will not prevent set the delay period to zero or any short period : 
So if the delay was set to a very short period and Someone gains control over a router and triggers a malicious ScheduleUpgrade message , the malicious attacker can trigger the executeScheduledRely() function after the delay period, which is too short, to give his address or any contract an auth role on any of the protocol contracts, the attacker can be auth on the escrow contract and steals all the funds from the protocol. 
This attack does not assume that the auth admin on the Root contract is malicious, but it is all about the possibility of setting the delay period to a very short period or even zero, which can be happened mistakenly or intentionally.  
This vulnerability can be mitigated by implementing a minimum threshold MIN_DELAY to the delay period, so this will prevent setting the delay period to zero or even a very short period. 
