There is a lot of concern within the IT industry right now around ransomware and many companies are taking steps to ensure they have applied the latest security patches provided by Microsoft. This is of course recommended and Qlik as a company applies these patches when they are made available.
Please note that we have seen some Windows patches which will enable or disable TLS and this protocol is used by QlikView server. The support team have published an article which should be read if you run in to issues such as "SSL: Decrypt Message Error". Article 0000025277 titled "QlikView Server Error "SSL: Decrypt Message Error" when using Digital Certificate communication between QlikView services" guides you on the steps to take if you see this issue after patching Windows.