Can forced shut down damage OS security?
Great Question!

There used to be a time when Mac's power button used to be known as certain death if you had to use it.

A forced shutdown does not damage your hardware, and neither does it weaken your security.

However, it could potentially corrupt your files if you are turning off the computer while they are open or being used (rather common in older models). These files can be anything, from a simple text file, to a bash script, or even to system files (ex. from an update). 

Because of this, there's no direct link between your system getting corrupted and your security being compromised. If your system has become corrupted to the point that services fail to load or critical files cannot be loaded (happens if you shutdown computers during intensive operations) you will most likely know about it because your computer will fail to boot, or throw errors.

A corruption in your computer will not suddenly open ports in your firewall, set your password to null, or let programs take over your computer and steal your identity.