Does it give you a string of numbers? Does it save privately to your account or Cloud? If using numbers, can anyone just type in random numbers or a long chain of numbers to potentially alter your game? If for instance game saves are 123456787, 123456788, 123456789 in sequence saves, it sort of leaves it open to the public. They may not know your string of numbers specifically, but they could jump around to other people’s work.
Which systems are you asking about?
Most of the online IF interpreters, like Parchment, save games in your browser local storage. (“Cookies”, basically.) They are never transmitted over the network so they can’t be seen by anybody else. (Or even by you on a different computer.)
Are you referring to Borogrove? If so, I don’t know the details but I’m pretty sure games are associated with the account you use to log in, so don’t think there’s a way to gain unauthorized access to works in progress through random typing. You can also make your game accessible only by a private link, rather than publishing to the main Borogrove page (I think this is how most people do it, actually).
I was just asking in general. I do not use online browsers, but for what ever reason that popped into my head. May have been a projecte I worked on years ago and I did not understand how the system worked. Maybe they were random numbers and not in any kind of guessable sequence. My apologies for being so vague.