The "Security" field is now invisible for some reason (no idea why, I haven't seen this mentioned anywhere), but it clearly still exists, and the value can't be changed (since it's invisible in the editor too).
H141 is blocking that. On the other hand, we may have Security tasks without Security, so we can:
- a) Disable H141, and have Security-Issues without Security or
- b) Enable changing this field at forms again, which would show this field for some people, or
- c) Make an edit-war with herald: H141 does only remove Security the first time, so if you remove it twice, you "win", that's why @matmarex failed to remove it, but @Paladox was able to do it.