If you’ve been keeping a large stack of macOS installers on hand, a number of them will need to be downloaded again as of today.
The security certificates for the macOS Sierra (10.12), macOS High Sierra (10.13), and macOS Mojave (10.14) operating systems expire today. This, in turn, can lead to errors stating that “This copy of the Install macOS Mojave.app application is damaged, and can’t be used to install macOS.”
The installers can be downloaded via the following links:
You’ll have to download the installers again to overcome this issue. Still, the new versions of the installers include updates that rolled out for the operating systems.
Via 9to5Mac and OSXDaily.com