I have set an option

  "CanOvenToggle": false,​

and player trying to toggle is getting the message from plugin, but toggle itself is not prevented.

For those, who possibly will have same problem: I removed all plugins and left only Prevent Looting to test and yes, this plugin works well. Then I continued to add plugins previously installed on my server and turns out the Quick Smelt is causing the issue.
Thanks for your plugin, and sorry for false alert.

For those who uses this plugin on server with Quick Smelt installed, here is workaround. You need to edit Quick Smelt code as follows. Find this code block:

        private object OnOvenToggle(StorageContainer oven, BasePlayer player)
        {
            if (oven is BaseFuelLightSource || oven.needsBuildingPrivilegeToUse && !player.CanBuild())
                return null;
			if(oven.OwnerID != player.userID) return null;

            PrintDebug("OnOvenToggle called");
            var component = oven.gameObject.GetComponent<FurnaceController>();
            var canUse = CanUse(oven.OwnerID) || CanUse(player.userID);
            if (oven.IsOn())
            {
                component.StopCooking();
            }
            else
            {
                if (canUse)
                    component.StartCooking();
                else
                {
                    PrintDebug($"No permission ({player.userID})");
                    return null;
                }
            }

            return false;
        }​

And replace it with this one:

        private object OnOvenToggle(StorageContainer oven, BasePlayer player)
        {
            if (oven is BaseFuelLightSource || oven.needsBuildingPrivilegeToUse && !player.CanBuild())
                return null;
            if(oven.OwnerID != player.userID)
            {
                BasePlayer owner = BasePlayer.FindByID(oven.OwnerID);
                if(owner == null) return null;
                if (owner.currentTeam == (long)0) return null;
                RelationshipManager.PlayerTeam playerTeam = RelationshipManager.Instance.FindTeam(player.currentTeam);
                if(!playerTeam.members.Contains(player.userID)) return null;
            }

            PrintDebug("OnOvenToggle called");
            var component = oven.gameObject.GetComponent<FurnaceController>();
            var canUse = CanUse(oven.OwnerID) || CanUse(player.userID);
            if (oven.IsOn())
            {
                component.StopCooking();
            }
            else
            {
                if (canUse)
                    component.StartCooking();
                else
                {
                    PrintDebug($"No permission ({player.userID})");
                    return null;
                }
            }

            return false;
        }​

This way only owner of oven or his teammate will have the ability to toggle oven.