Just make sure it's not the wank sock.

Probably? A fully cotton sock would be pretty safe.

My cat has her own little wheat bag that I microwave with the synthetic faux fur cover on and that hasn’t melted so far. (Though I usually give it one minute, maybe 1 min 30s, and never more than two - always removing it and checking it after the first minute).

However after reading up on this I probably will remove that cover before microwaving as polyester is a fire risk. https://www.reddit.com/r/sewing/comments/w6cedh/microwaveable_fabric/

I probably wouldn’t be microwaving wet cloth either which would create much more heat.~~(The occasional cup of water microwaved with it is to provide very slight humidity to the grains, not get the cloth wet.)~~ I also wouldn’t be microwaving anything for too long.

Edit: I retract the part about the cup of water, I was wrong https://www.wholesale.kiwiwheatbags.co.nz/pages/do-not-put-a-cup-of-water-in-the-microwave-when-heating-your-wheat-bag

The sock is more of a temporary or emergency solution though. Definitely consider buying a proper wheat bag of the proper materials that comes with specific usage instructions if you can afford to/justify the cost.