Why that? Here’s the only way to fix the problem, and how? Two new questions comes in front of you prior to when it actually assosiated. Back in February, Apple’s Worldwide Developer Certificate, designed specifically to verify third-party apps and services, expired, requiring Apple to issue a new certificate for developers to use. Apple hasn’t been having much luck with App Store certificates lately, with some crowd finding that they couldn’t launch any apps that had been bought via the online marketplace not so long ago. Found to be certificate-related issue, and now it appears that anyone who has an OS X installer all ready to go should something catastrophic happen will need to re-download it all over again, because, there’s a certificate problem.
Discoverd and pointed by TidBITS, the issue caused by an expired Mac App Store certificate that’s being used when the installers were created. Those OS X installation files downloaded from the store before Feb. 14, 2016 and stored on a computer or bootable USB flash drives are no longer functional. This includes installation files for OS X El Capitan and older versions of OS X like Mavericks and Mountain Lion, no way work.
Certificates of this kind are designed to ensure that the code that is being run has not been meddled with in any way by an attacker, and believe it or not, a sign that the certifiacte was actually working as it should, but the fact that an expired certificate will now allow an application or installer to to drive is a good thing. Fix for this issue is simple and what’s that? Users who can’t replace an expired certificate can still use older installers by changing the dates on their machines. Thankfully making this as easy as re-downloading your OS X installer of choice from the Mac App Store and recreating any installation media that yoy may have made in the past.
If you are in the middle of an OS X install and get tripped up by the expired certificate, Randy Singer offers a suggestion on how you can work around the problem quickly, without having to download a new installer:
1. In the OS X Installer, choose Utilities > Terminal.
2. Enter date 0201010116 and press Return.
3. Quit Terminal and continue the install.
That Terminal command sets your system date to 1 February 2016 — before the certificate’s expiration — so the installer can continue. Once you have completed the installation, visit System Preferences > Date & Time to reset the system date.
Apple quickly addressed the issue and has helped developers transition to the new certificate, which it caused multiple Mac App Store apps to display a “damaged” error and fail to open. If you’re new to bootable installation media, there are several tutorials to check out on how to make a bootable USB flash drive for the installation of OS X El Capitan.
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