It is possible to add invalid (empty or system) folders as project folders when using Add project from disk

How to reproduce (macOS):
1. Open Unity Hub
2. In the Projects tab, click on the “Add” dropdown and select the “Add project from disk” option
3. In the file browser window, select and open the “Applications” folder
4. Select any installed Unity Editor version (e.g., 6000.5.0a1, 6000.6.0a1, …) and click the “Open with …” button
5. Observe the Unity Editor

Actual result: The “/Applications” folder is added as a valid project folder, and in it an “Assets” folder is created and is opened in the Unity Editor
Expected result: You are not allowed to add the “/Applications” folder as a project folder

How to reproduce (Windows):
1. Open Unity Hub with Administrator privileges
2. In the Projects tab, click on the “Add” dropdown and select the “Add project from disk” option
3. In the file browser window, navigate to “C:\Windows\System32” select, and open the “System32” folder
4. Select any installed Unity Editor version (e.g., 6000.5.0a1, 6000.6.0a1, …) and click the “Open with …” button
5. Observe the Unity Editor

Actual result: The “System32” folder is added as a valid project folder, and in it an “Assets” folder is created and opened in the Unity Editor
Expected result: You are not allowed to add the “System32” folder as a project folder even if you give Unity Hub Administrator privileges

Reproducible with: 3.18.0

Reproducible on: Windows 11, macOS (M1) (25.4.0) by user
Not reproducible on: No other environments tested

Notes:

• You can also add any empty or non-empty folder; Unity Hub will create an “Assets” folder inside of it and launch it in the Unity Editor
• Trying to add the System32 on Windows or /Library on macOS folder without the required privileges will result in a silent failure