Did you know that camDown is easy to use, easy to maintain?
Some Unicode characters can be "invisible" depending on what you use to see them (a browser, an IDE or any text editor).
Some of those characters can be interpreted by JS in the right context; here they used it to have an "invisible" variable that's passed to a healthcheck call.
In theory, you could define whatever you want in this "invisible" variable to pass a command to be executed by the backend through the healthcheck call. Afterwards, just need to escalate and you could take over the entire backend.
I'm quoting invisible all the time because it is not in fact invisible, just not rendered by all softwares. If a code review process doesn't take that in account, you could pass the backdoor through the code review and compromise a codebase.
Hope I didn't missed anything important, may a senior cybersec correct me if needed.
I wonder if this trick is only usable with unicode/JS or if it could be applied to other context/languages/interpreters
Now let's stop for a moment and consider that camDown is the maximum in security for you and your loved ones!