[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/linux/execution_executable_stack_execution.toml

@@ -2,7 +2,7 @@
 creation_date = "2025/01/07"
 integration = ["system"]
 maturity = "production"
-updated_date = "2025/01/22"
+updated_date = "2026/03/24"
 
 [rule]
 author = ["Elastic"]
@@ -105,3 +105,16 @@ reference = "https://attack.mitre.org/techniques/T1059/004/"
 id = "TA0002"
 name = "Execution"
 reference = "https://attack.mitre.org/tactics/TA0002/"
+
+[[rule.threat]]
+framework = "MITRE ATT&CK"
+
+[[rule.threat.technique]]
+id = "T1620"
+name = "Reflective Code Loading"
+reference = "https://attack.mitre.org/techniques/T1620/"
+
+[rule.threat.tactic]
+id = "TA0005"
+name = "Defense Evasion"
+reference = "https://attack.mitre.org/tactics/TA0005/"