fix

app/vmagent/remotewrite/client_test.go

@@ -9,6 +9,7 @@ import (
 	"github.com/golang/snappy"
 
 	"github.com/VictoriaMetrics/VictoriaMetrics/lib/encoding"
+	"github.com/VictoriaMetrics/VictoriaMetrics/lib/flagutil"
 )
 
 func TestParseRetryAfterHeader(t *testing.T) {
@@ -36,6 +37,34 @@ func TestParseRetryAfterHeader(t *testing.T) {
 	f(time.Now().Add(10*time.Second).Format("Mon, 02 Jan 2006 15:04:05 FAKETZ"), 0)
 }
 
+func TestInitSecretFlags(t *testing.T) {
+	showRemoteWriteURLOrig := *showRemoteWriteURL
+	defer func() {
+		*showRemoteWriteURL = showRemoteWriteURLOrig
+		flagutil.UnregisterAllSecretFlags()
+	}()
+
+	flagutil.UnregisterAllSecretFlags()
+	*showRemoteWriteURL = false
+	InitSecretFlags()
+	if !flagutil.IsSecretFlag("remotewrite.url") {
+		t.Fatalf("expecting remoteWrite.url to be secret")
+	}
+	if !flagutil.IsSecretFlag("remotewrite.headers") {
+		t.Fatalf("expecting remoteWrite.headers to be secret")
+	}
+
+	flagutil.UnregisterAllSecretFlags()
+	*showRemoteWriteURL = true
+	InitSecretFlags()
+	if flagutil.IsSecretFlag("remotewrite.url") {
+		t.Fatalf("remoteWrite.url must remain visible when -remoteWrite.showURL is set")
+	}
+	if !flagutil.IsSecretFlag("remotewrite.headers") {
+		t.Fatalf("expecting remoteWrite.headers to remain secret")
+	}
+}
+
 func TestRepackBlockFromZstdToSnappy(t *testing.T) {
 	expectedPlainBlock := []byte(`foobar`)
 

app/vmagent/remotewrite/remotewrite.go

@@ -151,6 +151,8 @@ func InitSecretFlags() {
 		// remoteWrite.url can contain authentication codes, so hide it at `/metrics` output.
 		flagutil.RegisterSecretFlag("remoteWrite.url")
 	}
+	// remoteWrite.headers can contain auth headers such as Authorization and API keys.
+	flagutil.RegisterSecretFlag("remoteWrite.headers")
 }
 
 var (

docs/victoriametrics/changelog/CHANGELOG.md

@@ -26,6 +26,8 @@ See also [LTS releases](https://docs.victoriametrics.com/victoriametrics/lts-rel
 
 ## tip
 
+* BUGFIX: [vmagent](https://docs.victoriametrics.com/victoriametrics/vmagent/): hide values passed to `-remoteWrite.headers` in startup logs, `/metrics`, and `/flags`, since they can contain sensitive HTTP headers such as `Authorization` and API keys.
+
 ## [v1.140.0](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.140.0)
 
 Released at 2026-04-10