diff --git a/internal/api/alerts.go b/internal/api/alerts.go
index 00608f6..ea1704c 100644
--- a/internal/api/alerts.go
+++ b/internal/api/alerts.go
@@ -36,18 +36,24 @@ func (h *AlertHandlers) SetMonitor(m *monitoring.Monitor) {
 
 // validateAlertID validates an alert ID for security
 func validateAlertID(alertID string) bool {
-	// Check length to prevent DOS attacks with huge IDs
+	// Guard against empty strings or extremely large payloads that could impact memory usage.
 	if len(alertID) == 0 || len(alertID) > 500 {
 		return false
 	}
-	// Alert IDs should only contain alphanumeric, hyphens, underscores, colons, and slashes
-	// (e.g., "pve1:qemu/101-cpu", "node-offline-pve1")
-	for _, c := range alertID {
-		if !((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
-			(c >= '0' && c <= '9') || c == '-' || c == '_' || c == ':' || c == '/' || c == '.') {
+
+	// Reject attempts to traverse directories via crafted path segments.
+	if strings.Contains(alertID, "../") || strings.Contains(alertID, "/..") {
+		return false
+	}
+
+	// Permit any printable ASCII character (including spaces) so user supplied identifiers
+	// like instance names remain valid, while excluding control characters and DEL.
+	for _, r := range alertID {
+		if r < 32 || r == 127 {
 			return false
 		}
 	}
+
 	return true
 }
 
diff --git a/internal/api/alerts_test.go b/internal/api/alerts_test.go
new file mode 100644
index 0000000..2fe09a3
--- /dev/null
+++ b/internal/api/alerts_test.go
@@ -0,0 +1,37 @@
+package api
+
+import "testing"
+
+func TestValidateAlertID(t *testing.T) {
+	testCases := []struct {
+		name  string
+		id    string
+		valid bool
+	}{
+		{name: "basic", id: "guest-powered-off-pve-101", valid: true},
+		{name: "with spaces", id: "cluster one-node-101-cpu", valid: true},
+		{name: "with slash and colon", id: "pve1:qemu/101-cpu", valid: true},
+		{name: "empty", id: "", valid: false},
+		{name: "too long", id: string(make([]byte, 501)), valid: false},
+		{name: "control char", id: "bad\nvalue", valid: false},
+		{name: "path traversal", id: "../etc/passwd", valid: false},
+		{name: "path traversal middle", id: "pve/../secret", valid: false},
+	}
+
+	// Populate the oversized id string once to avoid zero bytes being mistaken for a valid character set.
+	for i := range testCases {
+		if testCases[i].name == "too long" {
+			value := make([]byte, 501)
+			for j := range value {
+				value[j] = 'a'
+			}
+			testCases[i].id = string(value)
+		}
+	}
+
+	for _, tc := range testCases {
+		if got := validateAlertID(tc.id); got != tc.valid {
+			t.Errorf("validateAlertID(%s) = %v, want %v", tc.name, got, tc.valid)
+		}
+	}
+}