An elevation of privilege vulnerability exists in Windows Text Service Framework (TSF) when the TSF server process does not validate the source of input or commands it receives, aka 'Windows Text Service Framework Elevation of Privilege Vulnerability'.
https://www.tenable.com/blog/microsofts-september-2019-patch-tuesday-tenable-roundup
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2019-1235