diff --git a/client/web/web.go b/client/web/web.go
index 2a2313a67..816890e2f 100644
--- a/client/web/web.go
+++ b/client/web/web.go
@@ -20,6 +20,7 @@
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"github.com/gorilla/csrf"
 	"tailscale.com/client/tailscale"
@@ -56,6 +57,18 @@ type Server struct {
 	cgiMode    bool
 	cgiPath    string
 	apiHandler http.Handler // csrf-protected api handler
+
+	selfMu sync.Mutex // protects self field
+	// self is a cached NodeView of the active self node,
+	// refreshed by watching the IPN notification bus
+	// (see Server.watchSelf).
+	//
+	// self's hostname and Tailscale IP are used to verify
+	// that incoming requests to the web client api are coming
+	// from the web client frontend and not some other source.
+	// Particularly to protect against DNS rebinding attacks.
+	// self should not be used to fill data for frontend views.
+	self tailcfg.NodeView
 }
 
 // ServerOpts contains options for constructing a new Server.
@@ -74,7 +87,8 @@ type ServerOpts struct {
 }
 
 // NewServer constructs a new Tailscale web client server.
-func NewServer(opts ServerOpts) (s *Server, cleanup func()) {
+// The provided context should live for the duration of the Server's lifetime.
+func NewServer(ctx context.Context, opts ServerOpts) (s *Server, cleanup func()) {
 	if opts.LocalClient == nil {
 		opts.LocalClient = &tailscale.LocalClient{}
 	}
@@ -97,6 +111,15 @@ func NewServer(opts ServerOpts) (s *Server, cleanup func()) {
 		csrfProtect := csrf.Protect(s.csrfKey(), csrf.Secure(false))
 		s.apiHandler = csrfProtect(&api{s: s})
 	}
+
+	var wg sync.WaitGroup
+	defer wg.Wait()
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		go s.watchSelf(ctx)
+	}()
+
 	s.lc.IncrementCounter(context.Background(), "web_client_initialization", 1)
 	return s, cleanup
 }
@@ -105,6 +128,58 @@ func init() {
 	tmpls = template.Must(template.New("").ParseFS(embeddedFS, "*"))
 }
 
+// watchSelf watches the IPN notification bus to refresh
+// the Server's self node cache.
+func (s *Server) watchSelf(ctx context.Context) {
+	watchCtx, cancelWatch := context.WithCancel(ctx)
+	defer cancelWatch()
+
+	watcher, err := s.lc.WatchIPNBus(watchCtx, ipn.NotifyInitialNetMap|ipn.NotifyNoPrivateKeys)
+	if err != nil {
+		log.Fatalf("lost connection to tailscaled: %v", err)
+	}
+	defer watcher.Close()
+
+	for {
+		n, err := watcher.Next()
+		if err != nil {
+			log.Fatalf("lost connection to tailscaled: %v", err)
+		}
+		if state := n.State; state != nil && *state == ipn.NeedsLogin {
+			s.updateSelf(tailcfg.NodeView{})
+			continue
+		}
+		if n.NetMap == nil {
+			continue
+		}
+		s.updateSelf(n.NetMap.SelfNode)
+	}
+}
+
+// updateSelf grabs the lock and updates s.self.
+// Then logs if anything changed.
+func (s *Server) updateSelf(self tailcfg.NodeView) {
+	s.selfMu.Lock()
+	prev := s.self
+	s.self = self
+	s.selfMu.Unlock()
+
+	var old, new tailcfg.StableNodeID
+	if prev.Valid() {
+		old = prev.StableID()
+	}
+	if s.self.Valid() {
+		new = s.self.StableID()
+	}
+	if old != new {
+		if new.IsZero() {
+			log.Printf("self node logout")
+		} else {
+			log.Printf("self node login")
+		}
+	}
+}
+
 // ServeHTTP processes all requests for the Tailscale web client.
 func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// some platforms where the client runs have their own authentication
diff --git a/cmd/tailscale/cli/web.go b/cmd/tailscale/cli/web.go
index d3daaa6c5..2758ba695 100644
--- a/cmd/tailscale/cli/web.go
+++ b/cmd/tailscale/cli/web.go
@@ -78,7 +78,7 @@ func runWeb(ctx context.Context, args []string) error {
 		return fmt.Errorf("too many non-flag arguments: %q", args)
 	}
 
-	webServer, cleanup := web.NewServer(web.ServerOpts{
+	webServer, cleanup := web.NewServer(ctx, web.ServerOpts{
 		DevMode:     webArgs.dev,
 		CGIMode:     webArgs.cgi,
 		LocalClient: &localClient,
diff --git a/tsnet/example/web-client/web-client.go b/tsnet/example/web-client/web-client.go
index 903088f23..52a0adff0 100644
--- a/tsnet/example/web-client/web-client.go
+++ b/tsnet/example/web-client/web-client.go
@@ -5,6 +5,7 @@
 package main
 
 import (
+	"context"
 	"flag"
 	"log"
 	"net/http"
@@ -20,6 +21,7 @@
 
 func main() {
 	flag.Parse()
+	ctx := context.Background()
 
 	s := new(tsnet.Server)
 	defer s.Close()
@@ -30,7 +32,7 @@ func main() {
 	}
 
 	// Serve the Tailscale web client.
-	ws, cleanup := web.NewServer(web.ServerOpts{
+	ws, cleanup := web.NewServer(ctx, web.ServerOpts{
 		DevMode:     *devMode,
 		LocalClient: lc,
 	})