This update resolves the following issue:
(http://support.microsoft.com/kb/2962975/ )
Lync 2013 starts and prompts you for credentials when you join meeting without account that is provisioned for Lync 2013

Additionally, this update also resolves the following issues:

Note To resolve the following issues, after you install update 2850074, you must install the security update 2881013:
(http://support.microsoft.com/kb/2881013/ )
MS14-036: Description of the security update for Microsoft Lync 2013: June 10, 2014
·         Lync 2013 crashes in a large meeting that many users have joined. Additionally, you may receive the following error message:
Problem signature
Problem Event Name: APPCRASH
Application Name: lync.exe
Application Version: Version number
Application Timestamp: Value
Fault Module Name: UccApi.dll
Fault Module Version: Version number
Fault Module Timestamp: Value
Exception Code: c0000005
Exception Offset: 001195a7
OS Version: Version number
Locale ID: 1033
 
·         Lync 2013 crashes in a meeting. This issue occurs when a meeting item is changing in the meeting list view model.
·         2968251(http://support.microsoft.com/kb/2968251/ )
Update adds an upload notification when you upload PPT in a meeting in Lync 2013
·         2968248
(http://support.microsoft.com/kb/2968248/ )
Lync 2013 video quality is low when you scale up the size of the video window in UI suppression mode
·         2968239
(http://support.microsoft.com/kb/2968239/ )
"An error occurred" error when a Lync 2013 user joins a Lync Online meeting that is created by a non-federated user
·         2962986
(http://support.microsoft.com/kb/2962986/ )
Lync 2013 takes a long time to sign in after it is disconnected from a front-end server
·         2962982
(http://support.microsoft.com/kb/2962982/ )
Caller's display name is not in the toast notification when you receive a call in Lync 2013
·         2962980
(http://support.microsoft.com/kb/2962980/ )
Lync 2013 prompts you for Exchange credential in an Exchange deployed environment