If you are working with macOS Catalina, when you install a Mac app that is not notarized by Apple you may be noted that: “The App will damage your computer. You should reject the disk image. This item is on the disk image “app.dmg”. Chrome downloaded this disk image today at 19.19 from xxx website.” And there are only two option to choose: eject disk image and cancel.
So, what’s the reason? The reason is that the improved features for the newest version of macOS Catalina that can better protect users’ Mac computers from malware and some suspicious software. If a Mac app that you download on the Internet has been not identified and reviewed by Apple, you will receive such message before it opens the first time on your Mac.
So, it seems like that there is no way to get your desired Mac app from a legitimate, trusted source installed on your Mac computer like usual. Actually, if you authorize this app and override security settings and it also can be installed on your Mac.
To allow a Mac app to be installed on your Mac, you should select the sources. macOS has 3 kinds of sources from which you will permit a Mac app to be installed:
Case 1: If the app that isn’t allowed to open is not provided by App Store but an identified developer, it will be very easy to override the security setting, you can refer to more details from this tutorial.
Case 2: If the app will damage your computer and you should eject the disk image, and you trust it and want to install it anyway, follow the steps as:
1. Click the Apple icon in the top-left corner of the desktop screen > Click System Preferences from the drop-down menu > Click the Security & Privacy option.
2. Click General tab> click on the lock icon to unlock it the current criteria. Next, The System Preferences is trying to unlock Security & Privacy preferences, enter your Password in the pop-up box to allow this and click Unlock.
3. For the latest version of macOS Catalina, you can’t see the option that allows app downloaded from Anywhere. To enable the Anywhere option, open Terminal and enter the following command.
4. After that, type your Password behind the flashing cursor > press Enter key to apply this changes.
Once done, the option of Anywhere will be enabled. You you will see the option of Anywhere appears in the General tab. If it is not checked, just need to adjust it.
This usually will solve the issue that the app will damage your computer and you should eject the disk image.