As documented under Secret user macros there are a few locations where the User macros of the type "Secret" are exposed/unmasked. Media types of type Script and Webhook are mentioned on this list.

We have the need to hide these information. When it is being sent to a third party tool (ITSM) via webhook the item key is included with all its parameters. Even if we are using Secret text to hide credentials used as parameters on the item key, it gets exposed.

We are aware of the possibility of using built-in macros such as {ITEM.KEY.ORIG}, which will show the Original key (with macros not expanded) of the Nth item in the trigger expression that caused a notification. But we are not interested to hide the content of all macros, just from macros using secret text.

We also tried using macro functions (regsub), but still not an ideal solution to it. 
The most interesting feature for this case would be to have a feature in Zabbix to disable secret macros from being exposed outside the Zabbix environment - in other words - in the Mediatype.