I failed (Oct 2020) the CISSP exam. I studied and was confident when going to take the exam; however, I did not practice taking tests or study while wearing my face mask. During the test I was distracted/frustrated by my glasses fogging up. I kept having to read and reread the questions. This caused me to feel time rushed. If you wear glasses...study and practice taking test with your face mask on.
Here's a trick I have picked up since I wear glasses.
Take a couple of pieces of surgical tape (the paper kind you can purchase in any drug store) and tape the top of the mask. It stops my glasses from fogging up.
Hope this helps.
I had the same problem while taking the CSSLP exam at Pearson VUE in Orlando, FL. I started the exam with no mask thinking it was OK to not have to wear a mask while at the testing station. A few minutes later, a proctor told me to put my mask on. Then the fogging started. I used a finger to extend the bridge of my nose to avoid the issue somewhat. It certainly wasn't comfortable. Fortunately I passed, so I won't have to go through that again for that certification. I'm prepping for CISSP now, so I know to practice with my mask on.
Use a clean cloth and smear a drop of dish soap on the lens. The film left behind isn't prone to temperature changes from hot breath.
Better luck on the exam next time!
You could also try motorcycle visor anti fog treatments which work by breaking the surface tension of water droplets as they form. If you have some laying about give it a try.
Suggest finding a mask that extends up higher on your nose so that your glasses rest comfortably atop the mask, preventing the fogging effect. Took me a couple attempts with different masks to find one that I felt both comfortable wearing and no longer fogged up my glasses.
On a personal note, I only started to need glasses in my earlier 50s so simply adjusting to glasses was enough to make my blood boil but tack on the mask thing and emotions really became irate for me.