Enabling high contrast mode via accessability settings can be used to bypass server resource pack limits

If you enable "High Contrast" in accessibility settings, the corresponding resource pack gets placed above any world-specific resource packs. From there, you can enable any other packs and sort them on top as well. You can use this to bypass any resource pack limits set in place by a server. For example, a server may have a designated resource pack used to prevent cheating via resource packs, but but by enabling the mentioned setting, you can ignore this and enable any packs you want.

Note this only works if the high contrast UI pack is enabled via accessability. Using the resource packs button works like normal.