Add validation for empty URL config

CHANGELOG.next.asciidoc

@@ -109,6 +109,7 @@ is collected by it.
 - Ensure winlog input retains metric collection when handling recoverable errors. {issue}36479[36479] {pull}36483[36483]
 - Revert error introduced in {pull}35734[35734] when symlinks can't be resolved in filestream. {pull}36557[36557]
 - Fix ignoring external input configuration in `take_over: true` mode {issue}36378[36378] {pull}36395[36395]
+- Add validation to http_endpoint config for empty URL {pull}36816[36816] {issue}36772[36772]
 
 *Heartbeat*
 

x-pack/filebeat/input/http_endpoint/config.go

@@ -110,6 +110,10 @@ func (c *config) Validate() error {
 		return errors.New("crc.provider is required when crc.secret is defined")
 	}
 
+	if c.URL == "" {
+		return fmt.Errorf("webhook path URL can not be empty")
+	}
+
 	return nil
 }
 

x-pack/filebeat/input/http_endpoint/config_test.go

@@ -0,0 +1,60 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package http_endpoint
+
+import (
+	"fmt"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_validateConfig(t *testing.T) {
+	testCases := []struct {
+		name      string // Sub-test name.
+		config    config // Load config parameters.
+		wantError error  // Expected error
+	}{
+		{
+			name: "invalid URL",
+			config: config{
+				URL:          "",
+				ResponseBody: `{"message": "success"}`,
+				Method:       http.MethodPost,
+			},
+			wantError: fmt.Errorf("webhook path URL can not be empty"),
+		},
+		{
+			name: "invalid method",
+			config: config{
+				URL:          "/",
+				ResponseBody: `{"message": "success"}`,
+				Method:       "random",
+			},
+			wantError: fmt.Errorf("method must be POST, PUT or PATCH: random"),
+		},
+		{
+			name: "invalid URL",
+			config: config{
+				URL:          "/",
+				ResponseBody: "",
+				Method:       http.MethodPost,
+			},
+			wantError: fmt.Errorf("response_body must be valid JSON"),
+		},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			tc.config.URL = ""
+			// Execute config validation
+			err := tc.config.Validate()
+
+			// Validate responses
+			assert.Equal(t, tc.wantError, err)
+		})
+	}
+}