My friend can open my Apple Iphone 13Pro Max with is Face ID; Accidently we came to know that my phone gets unlocked using his Face ; It sounds risky that someone else also can access the same. how can i address this issue to Apple ?
Try reset Face ID by going to Settings > Face ID & passcode > Reset Face ID.
If your friend can unlock the phone with his face after reset, I think there is a problem with the Face ID in your phone and it should be fixed.
And see this article to learn more about Face ID technology >>>About Face ID advanced technology - Apple Support
The article you linked to explicitly states:
The probability that a random person in the population could look at your iPhone or iPad Pro and unlock it using Face ID is approximately 1 in 1,000,000 with a single enrolled appearance. As an additional protection, Face ID allows only five unsuccessful match attempts before a passcode is required. The statistical probability is different for twins and siblings that look like you and among children under the age of 13, because their distinct facial features may not have fully developed. If you're concerned about this, we recommend using a passcode to authenticate.
So in fact, there may not be anything wrong with FaceID.
FACE ID activated by others
