diff --git a/.changes/next-release/enhancement-core-5xawlnap.json b/.changes/next-release/enhancement-core-5xawlnap.json
new file mode 100644
index 0000000..c7bd59a
--- /dev/null
+++ b/.changes/next-release/enhancement-core-5xawlnap.json
@@ -0,0 +1,5 @@
+{
+  "type": "enhancement",
+  "category": "core",
+  "description": "Guard --endpoint-url against sending the IAM bearer token to untrusted hosts (SEC-08): hosts outside vngcloud.vn/greenode.ai are warned over TLS, and blocked when there is no TLS protection (plain http or --no-verify-ssl) unless --allow-untrusted-endpoint is set"
+}
diff --git a/go/cmd/root.go b/go/cmd/root.go
index 6277601..402fd75 100644
--- a/go/cmd/root.go
+++ b/go/cmd/root.go
@@ -25,6 +25,7 @@ var (
 	CLIReadTimeout    int
 	CLIConnectTimeout int
 	Color             string
+	AllowUntrusted    bool
 )
 
 var rootCmd = &cobra.Command{
@@ -60,6 +61,7 @@ func init() {
 	rootCmd.PersistentFlags().StringVar(&Query, "query", "", "JMESPath query to filter output")
 	rootCmd.PersistentFlags().StringVar(&EndpointURL, "endpoint-url", "", "Override the service endpoint URL")
 	rootCmd.PersistentFlags().BoolVar(&NoVerifySSL, "no-verify-ssl", false, "Disable SSL certificate verification")
+	rootCmd.PersistentFlags().BoolVar(&AllowUntrusted, "allow-untrusted-endpoint", false, "Allow --endpoint-url to a host outside vngcloud.vn/greenode.ai without TLS protection (sends a bearer token there)")
 	rootCmd.PersistentFlags().BoolVar(&Debug, "debug", false, "Enable debug logging")
 	rootCmd.PersistentFlags().IntVar(&CLIReadTimeout, "cli-read-timeout", 30, "HTTP read timeout in seconds")
 	rootCmd.PersistentFlags().IntVar(&CLIConnectTimeout, "cli-connect-timeout", 30, "HTTP connect timeout in seconds")
diff --git a/go/internal/cli/client.go b/go/internal/cli/client.go
index b7be48d..b31a243 100644
--- a/go/internal/cli/client.go
+++ b/go/internal/cli/client.go
@@ -22,9 +22,14 @@ func NewClient(cmd *cobra.Command, serviceName string) (*client.GreenodeClient,
 	endpointURL, _ := cmd.Flags().GetString("endpoint-url")
 	noVerifySSL, _ := cmd.Flags().GetBool("no-verify-ssl")
 	debug, _ := cmd.Flags().GetBool("debug")
+	allowUntrusted, _ := cmd.Flags().GetBool("allow-untrusted-endpoint")
 	connectTimeout, _ := cmd.Flags().GetInt("cli-connect-timeout")
 	readTimeout, _ := cmd.Flags().GetInt("cli-read-timeout")
 
+	if err := CheckEndpoint(endpointURL, noVerifySSL, allowUntrusted); err != nil {
+		return nil, err
+	}
+
 	cfg, err := config.LoadConfig(profile)
 	if err != nil {
 		return nil, err
diff --git a/go/internal/cli/endpoint.go b/go/internal/cli/endpoint.go
new file mode 100644
index 0000000..0b7c5a9
--- /dev/null
+++ b/go/internal/cli/endpoint.go
@@ -0,0 +1,70 @@
+package cli
+
+import (
+	"fmt"
+	"net/url"
+	"os"
+	"strings"
+)
+
+// trustedEndpointDomains are the domains grn's own services live under. A
+// request to a host outside these is flagged because grn sends a reusable IAM
+// bearer token with every request (see CheckEndpoint / SEC-08).
+var trustedEndpointDomains = []string{"vngcloud.vn", "greenode.ai"}
+
+// IsTrustedEndpoint reports whether endpointURL targets a host within a trusted
+// domain. An empty value means no --endpoint-url override was given (the
+// built-in region endpoint is used), which is trusted.
+func IsTrustedEndpoint(endpointURL string) bool {
+	if endpointURL == "" {
+		return true
+	}
+	u, err := url.Parse(endpointURL)
+	if err != nil {
+		return false
+	}
+	host := u.Hostname()
+	if host == "" {
+		return false
+	}
+	for _, d := range trustedEndpointDomains {
+		if host == d || strings.HasSuffix(host, "."+d) {
+			return true
+		}
+	}
+	return false
+}
+
+// CheckEndpoint enforces the endpoint-safety policy for --endpoint-url. grn
+// authenticates against the real IAM and sends the resulting reusable bearer
+// token to whatever host --endpoint-url names, so:
+//   - trusted host (or no override): allowed silently.
+//   - untrusted host over TLS (https, cert verified): a warning is printed.
+//   - untrusted host without TLS protection (plain http, or --no-verify-ssl):
+//     blocked with an error unless allowUntrusted is set, because the token can
+//     be captured (MITM) and replayed.
+//
+// It returns a non-nil error only for the blocked case.
+func CheckEndpoint(endpointURL string, noVerifySSL, allowUntrusted bool) error {
+	if IsTrustedEndpoint(endpointURL) {
+		return nil
+	}
+	u, _ := url.Parse(endpointURL)
+	host := u.Hostname()
+
+	noTLS := noVerifySSL || strings.EqualFold(u.Scheme, "http")
+	if noTLS && !allowUntrusted {
+		reason := "plain HTTP"
+		if noVerifySSL {
+			reason = "--no-verify-ssl"
+		}
+		return fmt.Errorf(
+			"refusing to send your IAM bearer token to untrusted host %q over an unprotected connection (%s): the token could be captured and replayed. Re-run with --allow-untrusted-endpoint if you really intend this",
+			host, reason)
+	}
+
+	fmt.Fprintf(os.Stderr,
+		"Warning: --endpoint-url %q is outside the trusted domains (%s). grn will send your IAM bearer token to this host, and a bearer token can be replayed. Only use endpoints you trust.\n",
+		host, strings.Join(trustedEndpointDomains, ", "))
+	return nil
+}
diff --git a/go/internal/cli/endpoint_test.go b/go/internal/cli/endpoint_test.go
new file mode 100644
index 0000000..006df34
--- /dev/null
+++ b/go/internal/cli/endpoint_test.go
@@ -0,0 +1,49 @@
+package cli
+
+import "testing"
+
+func TestIsTrustedEndpoint(t *testing.T) {
+	cases := map[string]bool{
+		"":                                      true, // no override -> built-in endpoint
+		"https://vks.api.vngcloud.vn":           true,
+		"https://hcm-3.api.vngcloud.vn/x":       true,
+		"https://vngcloud.vn":                   true,
+		"https://api.greenode.ai":               true,
+		"https://greenode.ai":                   true,
+		"http://attacker.com":                   false,
+		"https://evil.vngcloud.vn.attacker.com": false, // suffix must be a real domain boundary
+		"https://notgreenode.ai":                false, // must match on a dot boundary
+		"http://localhost:8080":                 false,
+		"not-a-url ::::":                        false,
+	}
+	for in, want := range cases {
+		if got := IsTrustedEndpoint(in); got != want {
+			t.Errorf("IsTrustedEndpoint(%q) = %v, want %v", in, got, want)
+		}
+	}
+}
+
+func TestCheckEndpointPolicy(t *testing.T) {
+	cases := []struct {
+		name           string
+		endpoint       string
+		noVerifySSL    bool
+		allowUntrusted bool
+		wantBlocked    bool
+	}{
+		{"trusted https", "https://vks.api.vngcloud.vn", false, false, false},
+		{"trusted greenode", "https://api.greenode.ai", false, false, false},
+		{"no override", "", false, false, false},
+		{"untrusted https verified -> warn only", "https://custom.example.com", false, false, false},
+		{"untrusted http -> block", "http://attacker.com", false, false, true},
+		{"untrusted https + no-verify -> block", "https://attacker.com", true, false, true},
+		{"untrusted http + allow -> warn", "http://attacker.com", false, true, false},
+		{"untrusted https + no-verify + allow -> warn", "https://attacker.com", true, true, false},
+	}
+	for _, tc := range cases {
+		err := CheckEndpoint(tc.endpoint, tc.noVerifySSL, tc.allowUntrusted)
+		if (err != nil) != tc.wantBlocked {
+			t.Errorf("%s: blocked=%v, want %v (err=%v)", tc.name, err != nil, tc.wantBlocked, err)
+		}
+	}
+}
diff --git a/go/internal/vserverclient/client.go b/go/internal/vserverclient/client.go
index f93f000..441064d 100644
--- a/go/internal/vserverclient/client.go
+++ b/go/internal/vserverclient/client.go
@@ -7,6 +7,7 @@ import (
 
 	"github.com/spf13/cobra"
 	"github.com/vngcloud/greennode-cli/internal/auth"
+	"github.com/vngcloud/greennode-cli/internal/cli"
 	"github.com/vngcloud/greennode-cli/internal/client"
 	"github.com/vngcloud/greennode-cli/internal/config"
 	"github.com/vngcloud/greennode-cli/internal/formatter"
@@ -19,9 +20,14 @@ func BuildClient(cmd *cobra.Command) (*client.GreenodeClient, *config.Config, er
 	endpointURL, _ := cmd.Flags().GetString("endpoint-url")
 	noVerifySSL, _ := cmd.Flags().GetBool("no-verify-ssl")
 	debug, _ := cmd.Flags().GetBool("debug")
+	allowUntrusted, _ := cmd.Flags().GetBool("allow-untrusted-endpoint")
 	connectTimeout, _ := cmd.Flags().GetInt("cli-connect-timeout")
 	readTimeout, _ := cmd.Flags().GetInt("cli-read-timeout")
 
+	if err := cli.CheckEndpoint(endpointURL, noVerifySSL, allowUntrusted); err != nil {
+		return nil, nil, err
+	}
+
 	cfg, err := config.LoadConfig(profile)
 	if err != nil {
 		return nil, nil, err