What is the reason for the appearance of this page

[Moderator moved from Using the Community forums to Creative Cloud Services.]

Your operating system is asking for permission to access your keychain.  It's part of Apple's User Account Control system to verify your CC subscription's ID & password.   It's normal & expected behavior, nothing to be distressed about. 

did you exit your cc desktop app?

https://community.adobe.com/t5/creative-cloud-services-discussions/why-adobe-wants-to-use-the-local-items-keychain/td-p/11803803