Phonebook and HTTP 401 Authentication

[AMount]

Hello,

I have provisioning set up for numerous models (T19, T2x, T3x, T4x, T5x) and have seen a change since upgrading to v81.

Phones running v80 would re-request the remote phone book XML file when challenged by the server with an HTTP 401 response:

Code:

xxx.xxx.32.196 - - [27/Jun/2017:13:12:15 -0700] "GET /001565xxxxxx-phonebook.xml HTTP/1.1" 401 4012 "-" "Yealink SIP-T23G 44.80.0.95 00:15:65:xx:xx:xx"
xxx.xxx.32.196 - - [27/Jun/2017:13:12:15 -0700] "GET /001565xxxxxx-phonebook.xml HTTP/1.1" 200 6586 "-" "Yealink SIP-T23G 44.80.0.95 00:15:65:xx:xx:xx"

But when the same model running v81 is challenged by an HTTP 401 response, the phone considers it an error and stops trying to retrieve the file:

Code:

xx.xxx.83.129 - - [27/Jun/2017:13:39:34 -0700] "GET /001565xxxxxx-phonebook.xml HTTP/1.1" 401 4208 "-" "Yealink SIP-T23G 44.81.0.110 00:15:65:xx:xx:xx"

The phone does not present credentials to the server, and it doesn't try to retrieve the file again.

The phones should present credentials to the server when challenged. Otherwise the data is insecure.

Is this a bug? If not, why was this functionality removed?