Steps to Reproduce (there's multiple ways, here's my way):
1. do the /give command to give yourself armor with the Unbreakable tag

2. Use an anvil to enchant the Curse of Binding Book on it
3. Now you can wear it and it can't come off unless you die if /gamerule keepinventory is false meaning you can have to lose valuable armor as a result of this.
Since it's got the unbreakable tag you aren't able to get rid of the armor by letting the durability wear off which was how it was intended in the first place. It acts basically like Curse of Vanishing but with Armor which was definitely not intentional.
The proof I have shows me getting hit by a spider with the armor on and it shows that the durability doesn't drop thus not being able to take off armor that way.