Photoshop installer Error: can’t be opened because Apple cannot check it for malicious software

[AllyPS]

After I downloaded Photoshop_installer.dmg, I received Error message: “Photoshop Installer.app” can’t be opened because Apple cannot check it for malicious software. This software needs to be updated. Contact the developer for more information.  This item is on the disk image “Photoshop_Installer.dmg”. Safari downloaded this disk image today at 12:51 PM from creativecloud.adobe.com.

[Test Screen Name]

Exactly how did you get to this installer, please? Normally people are directed to download Creative Cloud instead. This sounds like an old file.