[Rule Tuning] Add Supplemental Mitre Mappings (#5876)

---------

Co-authored-by: Ruben Groenewoud <78494512+Aegrah@users.noreply.github.com>
Co-authored-by: Isai <59296946+imays11@users.noreply.github.com>
Co-authored-by: terrancedejesus <terrance.dejesus@elastic.co>
Co-authored-by: Jonhnathan <26856693+w0rk3r@users.noreply.github.com>
Co-authored-by: eric-forte-elastic <eric.forte@elastic.co>

rules/windows/initial_access_potential_webhelpdesk_exploit.toml

@@ -2,7 +2,7 @@
 creation_date = "2026/02/02"
 integration = ["endpoint"]
 maturity = "production"
-updated_date = "2026/02/09"
+updated_date = "2026/03/24"
 
 [rule]
 author = ["Elastic"]
@@ -92,14 +92,59 @@ any where host.os.type == "windows" and
 
 [[rule.threat]]
 framework = "MITRE ATT&CK"
+
 [[rule.threat.technique]]
 id = "T1190"
 name = "Exploit Public-Facing Application"
 reference = "https://attack.mitre.org/techniques/T1190/"
 
-
 [rule.threat.tactic]
 id = "TA0001"
 name = "Initial Access"
 reference = "https://attack.mitre.org/tactics/TA0001/"
 
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1218"
+name = "System Binary Proxy Execution"
+reference = "https://attack.mitre.org/techniques/T1218/"
+
+[[rule.threat.technique.subtechnique]]
+id = "T1218.011"
+name = "Rundll32"
+reference = "https://attack.mitre.org/techniques/T1218/011/"
+
+[rule.threat.tactic]
+id = "TA0005"
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1059"
+name = "Command and Scripting Interpreter"
+reference = "https://attack.mitre.org/techniques/T1059/"
+
+[[rule.threat.technique.subtechnique]]
+id = "T1059.001"
+name = "PowerShell"
+reference = "https://attack.mitre.org/techniques/T1059/001/"
+
+[[rule.threat.technique.subtechnique]]
+id = "T1059.003"
+name = "Windows Command Shell"
+reference = "https://attack.mitre.org/techniques/T1059/003/"
+
+[[rule.threat.technique]]
+id = "T1129"
+name = "Shared Modules"
+reference = "https://attack.mitre.org/techniques/T1129/"
+
+[rule.threat.tactic]
+id = "TA0002"
+name = "Execution"
+reference = "https://attack.mitre.org/tactics/TA0002/"