diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..0081571
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2025-03-05 - Windows Command Injection via subprocess.call
+**Vulnerability:** Command Injection vulnerability exists when using `subprocess.call(['start', filename], shell=True)` because `shell=True` on Windows allows attackers to execute arbitrary shell commands if the filename contains shell metacharacters (e.g. `&` or `^`), even if it passes `os.path.isfile()`.
+**Learning:** Checking if a file exists (`os.path.isfile()`) is insufficient to prevent command injection on Windows when `shell=True` is used, because legal Windows filenames can contain metacharacters that the shell interprets.
+**Prevention:** Always prefer `os.startfile(filename)` over `subprocess.call` with `shell=True` for opening files on Windows.
diff --git a/libs/utility_manager.py b/libs/utility_manager.py
index e62d1a5..95de28f 100644
--- a/libs/utility_manager.py
+++ b/libs/utility_manager.py
@@ -43,7 +43,7 @@ def _open_resource_file(self, filename):
 		try:
 			if os.path.isfile(filename):
 				if platform.system() == "Windows":
-					subprocess.call(['start', filename], shell=True)
+					os.startfile(filename)
 				elif platform.system() == "Darwin":
 					subprocess.call(['open', filename])
 				elif platform.system() == "Linux":