clipboard not working after Security Update
I had a similar situation, though it was caused by a sudden power-down in my case. Copy did not work in any of the apps I tried - viewing clipboard showed it to be empty. Restarting or logging out and logging in did not help. After several hours I stumbled onto an answer, which helped me.

In short, run in Terminal command, which rebuilds a cache of shared system services.

sudo update_dyld_shared_cache


Probably I restarted my Mac after that.