Consider the following scenario in a Microsoft Skype for Business Server 2015 environment:
You schedule a Microsoft Skype for Business meeting.
The meeting URL is posted somewhere publicly online.
In this scenario, when you search for "Skype for Business Web App" in search engines such as Google, Bing or Yahoo, you can see the meeting URL publicly.
Additionally, other people can join the meeting randomly if you enable the anonymous meeting join feature.
This issue occurs because search engines browse the public site, see the meet.lync.com URL, then crawl it, and index it into the search engines.
To fix this issue, install the December 2017 cumulative update 6.0.9319.510 for Skype for Business Server 2015, Web Components Server.
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