This simply is not viable. If you are giving anyone even read access to your game in studio they can steal all of your work because the source for everything is still directly replicated to their computer.
Your situation is unfortunate, but I guess you will have to be more careful next time.
I actually ran into this on accident prior to the announcement because my friend said “hey, you can change the player number on our game right?” (The game was on his account, but I was in the team create for it.) I told him I couldn’t because I’m not the owner and can’t configure the game, but then suddenly realized I could.
Much appreciated update, as now I can fix when my buddy is being lazy and not updating the thumbnail picture 
FINALLY
Ive been waiting for this feature for so long! Thank you!
Up until two weeks ago, this was my favorite addition to the developer-oriented feature catalog.
The ability to add groups to my user-made games as players or developers, and the ability to add individual users to my group games was a life-saving feature. I am saddened that this has been removed, as this effectively makes this feature useless for me.
I hope to see this extremely important feature added back, as it aided development.
PS: I would also like to note the extreme importance of group-rank based permissions for packages, as I often wish to share a code library with developers of a certain group, and the best way to dynamically do so is to add them by group rank.
Finally, a new feature has arrived! The feature is going to be very helpful and useful for everyone; as for giving permissions, collaborating, the Play feature and other features will be such an amazing idea, and I can’t wait to use this. 
With the permission of the new feature, it’ll be also a great and helpful idea for your friends and by everyone to test out your own game, which can get very exciting for the update!
Thank you developers for making the new feature, and I hope more features arrives in the future on Roblox! 
A big improvement will be if you’re allowed to add groups to another group game in the permissions instead of limited to 1 group. For example;
We have group A and Group B,
Group A
Is our official group that has all role sets from fans to testers and everything else. It’s also the location were our official released games are located.
Group B
In group B we have all games and updates that are in development. This is also the group for our official testers.
In the early testing of this feature you were allowed to add “Group A” to “Group B” permissions so we could allow the testers in Group A access to the games in Group B. But it seems it has now been removed officially. I made originally a report of it here but it seems it wasn’t a bug but intended.
But for us it was very useful and important that we can add other groups to the game permissions of another group. Because we have multiple groups for diffirent testing reasons. And we don’t want to require all testers being in multiple groups.
I have a question about this, So if i wanted somebody else besides me to advertise a group game, can this be used to have it so users with the permission to create + edit group games to be able to run game ads wouldnt be able to do specific things on studio by having the play permission toggled?
Does this mean we can expect recurring group payouts by game in the near future?
love it just gotta say one thing, can you add a permission where they would be able to change the lighting cause I worked with some people and they kept on ruining the lighting.
This is a much needed update, thanks again Roblox 
The update will come especially handy for game translators, allowing them only to translate 
I think what you’re saying is correct, but there is also big chance it’s not and we both misunderstood. What I’m saying is I know nothing.
Interesting, does the permissions tab automatically override group game permissions like to play or edit? Thanks.
It’s exactly the same thing, so yes.
When will the time come that collaborators on User-Owned games get to access the developer console? If this is fixed I am unaware of the update and would like the link to the post for said update. Thank you.
I think this is already accounted for, I have server console access on a few games I have team create access in.
I’m glad Roblox is moving towards a more thorough permissions interface for games, this is a really helpful change, however I’ve got two questions about the “Old” and “New” permissions table
“Shutdown All Servers” is shown as disabled in old permissions, yet I’ve always been able to shutdown all servers on games I do not own that I have access to. Am I missing something here?
Will these permissions be editable in the future? It would very helpful to be able to toggle certain features by the user or roleset such as the ability to save the place locally, rename the place, or publish the place.
Is it because i’m enrolled in the beta program that i’ve had these features for around 2 months now?
The beta program doesn’t affect studio anymore.
If you don’t remember enabling it, then there’s a potential it was enabled by default since it’s not a feature that replaces an existing functionality, but only an addition.
I can’t add players, the option does not even show.
I feel like the “Play” option will confuse new players because they feel like if the permission is not set to play, that user can’t play the game at all and they have to set everyone’s permission to play so people can play the game.