I have no idea why, but today I notized that some users I shared the QR-Code with had full access to the project. Meaning they could change settings, stop the project or edit it.
I shared the code again and the problem was gone.
Any ideas why that happened?
Shouldn’t be the case.
Any particular details?
Did all of them/some of them get access?
Can you share what phone and app version they use?
Blynk 2.10.1 on a Samsung Galaxy S7 Edge with Android 7.
He got a new phone, so I gave him the QR-Code again. Then he had full access.
After sharing it again he was a normal user.
I think I understand what might have happened… saving and scanning the QR code is how I backup and transfer my projects between Cloud and Local servers.
If you share, using the “master” device’s app, the receiving app treats the QR differently (or it contains different info?), giving limited rights.
But if you just scanned the saved-to-file QR code, then yes, it is as if you are restoring your full project. However, I would have assumed he would have needed your login/password as well? Or does he have his own account?
In the project settings I clicked on “Generate Link”.
He scanned the QR-Code that was on the screen.
That’s all.
(He has no account.)
Well, I myself have no idea then… there should be no way he could have edited it since he didn’t log in and there is no start/stop button on a Shared QR (not to be confused with a Cloned then shared QR).
You are sure you didn’t hit the Clone option, lower down on that same screen?? It also brings up a QR to scan (and/or share with others)… and will be a full access, but will require a login first… perhaps your friend knew your login??
I’m sure I hit the share button.
And even if the project ist cloned the project that is open on my phone should not behave exactly the same as on the other phone (stopped when he clicked stop), right?
I don’t think he knows my loggin data. It consists of a tangle of characters. 
He would have had full control over any running widgets… but there should not have even been been a “stop” option.
Right. If your observations correct (specifically that you did not stop the project yourself), then this was a bug. We’ll try to catch it.
We had some bug with project’s stop in case of logout from the master app (and it was fixed several app’s version ago), but there is no support for widget’s settings edit in shared apps or any other actions.
@Matti Are you sure that your friend has changed some widget’s settings (label, pin, etc) and it that changes were synced with your project?
He could go to the widget settings. He didn’t change anything in the settings, but as I wrote, he stopped the project and it stopped on my phone too.
