Suspicious RDP ActiveX Client Loaded

any where host.os.type == "windows" and
 (event.category : ("library", "driver") or (event.category == "process" and event.action : "Image loaded*")) and
 (?dll.name : "mstscax.dll" or file.name : "mstscax.dll") and
   /* depending on noise in your env add here extra paths  */
  process.executable : (
    "C:\\Windows\\*",
    "C:\\Users\\Public\\*",
    "C:\\Users\\Default\\*",
    "C:\\Intel\\*",
    "C:\\PerfLogs\\*",
    "C:\\ProgramData\\*",
    "\\Device\\Mup\\*",
    "\\\\*"
  ) and
  /* add here FPs */
  not process.executable : (
    "?:\\Windows\\System32\\mstsc.exe",
    "?:\\Windows\\SysWOW64\\mstsc.exe",
    "?:\\Windows\\System32\\vmconnect.exe",
    "?:\\Windows\\System32\\WindowsSandboxClient.exe",
    "?:\\Windows\\System32\\hvsirdpclient.exe"
  )