If you currently have mitigations enabled for the Spectre Variant 2 (CVE-2017-5715) vulnerability, Microsoft has now enabled the Retpoline Spectre mitigation feature by default in Windows 10 version 1809 (October 2018 Update) for better performance. […]

from https://www.bleepingcomputer.com/news/security/windows-10-spectre-2-mitigation-now-uses-retpoline-by-default/