Hi @Priya Jayaraman ,
At present, we did not find any known issue on Skype for Business 2015 CU 11 HF1. The following link lists all the updates for Skype for Business 2015:
https://paul-lange.net/updates-for-skype-for-business-server-2015/
For more details about installation instruction, you can learn it from:
https://support.microsoft.com/en-us/help/3061064/updates-for-skype-for-business-server-2015
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