Announcement for users on Mac OS X Yosemite v10.10: Photoshop, Illustrator, and InDesign will no longer support the operating system after the October 2017 release. For the best and most secure experience of these apps, we recommend using a supported operating system: OS X El Capitan v10.11, or macOS Sierra v.10.12.
What does this mean for you?
You can continue to install and use Photoshop, Illustrator, and InDesign on Mac OS X 10.10. However, Adobe will no longer test releases or patches for these operating systems, nor will any bugs specific to these operating systems be addressed. Furthermore, any future security updates or patches won’t be applicable to you. If you are entitled to support, Adobe will continue to support you, unless the problem you’re experiencing is isolated to Mac OS X Yosemite v10.10.
If you have any questions about this change, you can post them to Adobe forum for the community of users and experts.