diff --git a/auth/authentication.go b/auth/authentication.go
index 08ff8a0d7..6d8338f92 100644
--- a/auth/authentication.go
+++ b/auth/authentication.go
@@ -2,6 +2,7 @@ package auth
 
 import (
 	"errors"
+	"net/http"
 	"strings"
 	"time"
 
@@ -40,6 +41,7 @@ type Database interface {
 type Auth struct {
 	DB           Database
 	SecureCookie bool
+	CrossOrigin  *http.CrossOriginProtection
 }
 
 // RequireAdmin requires an elevated client token or basic auth, the user must be an admin.
@@ -87,6 +89,9 @@ func (a *Auth) Optional(ctx *gin.Context) {
 }
 
 func (a *Auth) evaluate(ctx *gin.Context, funcs ...func(ctx *gin.Context) (authState, error)) bool {
+	if a.rejectForeignOrigin(ctx) {
+		return true
+	}
 	for _, fn := range funcs {
 		state, err := fn(ctx)
 		if err != nil {
@@ -128,6 +133,17 @@ func (a *Auth) abort403(ctx *gin.Context) {
 	ctx.AbortWithError(403, errors.New("you are not allowed to access this api"))
 }
 
+func (a *Auth) rejectForeignOrigin(ctx *gin.Context) bool {
+	if _, isCookie := a.readTokenFromRequest(ctx); !isCookie {
+		return false
+	}
+	if err := a.CrossOrigin.Check(ctx.Request); err != nil {
+		ctx.AbortWithError(403, err)
+		return true
+	}
+	return false
+}
+
 func (a *Auth) handleUser(checks ...func(*model.User) (authState, error)) func(ctx *gin.Context) (authState, error) {
 	return func(ctx *gin.Context) (authState, error) {
 		if name, pass, ok := ctx.Request.BasicAuth(); ok {
diff --git a/auth/authentication_test.go b/auth/authentication_test.go
index f47fd9893..d92ecf10f 100644
--- a/auth/authentication_test.go
+++ b/auth/authentication_test.go
@@ -29,7 +29,7 @@ type AuthenticationSuite struct {
 func (s *AuthenticationSuite) SetupSuite() {
 	mode.Set(mode.TestDev)
 	s.DB = testdb.NewDB(s.T())
-	s.auth = &Auth{DB: s.DB}
+	s.auth = &Auth{DB: s.DB, CrossOrigin: http.NewCrossOriginProtection()}
 
 	now := time.Date(2025, 1, 1, 12, 0, 0, 0, time.UTC)
 	timeNow = func() time.Time { return now }
@@ -354,4 +354,65 @@ func (s *AuthenticationSuite) assertHeaderRequest(key, value string, f fMiddlewa
 	return ctx
 }
 
+func (s *AuthenticationSuite) TestCookieCrossOriginProtection() {
+	// httptest sets the request host to example.com.
+	s.assertCsrfRequest(map[string]string{"Origin": "http://example.com"}, "clienttoken", s.auth.RequireClient, 200)
+	s.assertCsrfRequest(map[string]string{"Origin": "https://example.com"}, "clienttoken", s.auth.RequireClient, 200)
+
+	s.assertCsrfRequest(map[string]string{"Origin": "http://evil.com"}, "clienttoken", s.auth.RequireClient, 403)
+	s.assertCsrfRequest(map[string]string{"Origin": "https://example.com.evil.com"}, "clienttoken", s.auth.RequireClient, 403)
+	s.assertCsrfRequest(map[string]string{"Origin": "null"}, "clienttoken", s.auth.RequireClient, 403)
+
+	s.assertCsrfRequest(nil, "clienttoken", s.auth.RequireClient, 200)
+
+	s.assertCsrfRequest(map[string]string{"Sec-Fetch-Site": "same-origin"}, "clienttoken", s.auth.RequireClient, 200)
+	s.assertCsrfRequest(map[string]string{"Sec-Fetch-Site": "none"}, "clienttoken", s.auth.RequireClient, 200)
+	s.assertCsrfRequest(map[string]string{"Sec-Fetch-Site": "cross-site"}, "clienttoken", s.auth.RequireClient, 403)
+	s.assertCsrfRequest(map[string]string{"Sec-Fetch-Site": "same-site"}, "clienttoken", s.auth.RequireClient, 403)
+
+	s.assertCsrfRequest(map[string]string{"Sec-Fetch-Site": "cross-site"}, "clienttoken_admin_elevated", s.auth.RequireElevatedClient, 403)
+	s.assertCsrfRequest(map[string]string{"Sec-Fetch-Site": "same-origin"}, "clienttoken_admin_elevated", s.auth.RequireElevatedClient, 200)
+}
+
+func (s *AuthenticationSuite) TestCrossOriginProtectionIgnoredForTokenAuth() {
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+	ctx.Request = httptest.NewRequest("POST", "/", nil)
+	ctx.Request.Header.Set("X-Gotify-Key", "clienttoken")
+	ctx.Request.Header.Set("Sec-Fetch-Site", "cross-site")
+	s.auth.RequireClient(ctx)
+	assert.Equal(s.T(), 200, recorder.Code)
+
+	recorder = httptest.NewRecorder()
+	ctx, _ = gin.CreateTestContext(recorder)
+	ctx.Request = httptest.NewRequest("POST", "/?token=clienttoken", nil)
+	ctx.Request.Header.Set("Sec-Fetch-Site", "cross-site")
+	s.auth.RequireClient(ctx)
+	assert.Equal(s.T(), 200, recorder.Code)
+}
+
+func (s *AuthenticationSuite) TestCrossOriginProtectionAllowsSafeMethods() {
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+	ctx.Request = httptest.NewRequest("GET", "/", nil)
+	ctx.Request.AddCookie(&http.Cookie{Name: cookieName, Value: "clienttoken"})
+	ctx.Request.Header.Set("Sec-Fetch-Site", "cross-site")
+	s.auth.RequireClient(ctx)
+	assert.Equal(s.T(), 200, recorder.Code)
+}
+
+func (s *AuthenticationSuite) assertCsrfRequest(headers map[string]string, cookie string, f fMiddleware, code int) {
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+	ctx.Request = httptest.NewRequest("POST", "/", nil)
+	if cookie != "" {
+		ctx.Request.AddCookie(&http.Cookie{Name: cookieName, Value: cookie})
+	}
+	for k, v := range headers {
+		ctx.Request.Header.Set(k, v)
+	}
+	f(ctx)
+	assert.Equal(s.T(), code, recorder.Code)
+}
+
 type fMiddleware gin.HandlerFunc
diff --git a/model/message.go b/model/message.go
index 6f75fe278..b18273954 100644
--- a/model/message.go
+++ b/model/message.go
@@ -32,7 +32,7 @@ type MessageExternal struct {
 	// read only: true
 	// required: true
 	// example: 5
-	ApplicationID uint `json:"appid"`
+	ApplicationID uint `form:"appid" query:"appid" json:"appid"`
 	// The message. Markdown (excluding html) is allowed.
 	//
 	// required: true
@@ -74,7 +74,7 @@ type CreateMessage struct {
 	// The application id that send this message. Always set when returned via the API.
 	//
 	// example: 5
-	ApplicationID uint `json:"appid"`
+	ApplicationID uint `form:"appid" query:"appid" json:"appid"`
 	// The message. Markdown (excluding html) is allowed.
 	//
 	// required: true
diff --git a/router/router.go b/router/router.go
index a32933954..cf4d8da46 100644
--- a/router/router.go
+++ b/router/router.go
@@ -84,7 +84,11 @@ func Create(db *database.GormDatabase, vInfo *model.VersionInfo, conf *config.Co
 			}
 		}
 	}()
-	authentication := auth.Auth{DB: db, SecureCookie: conf.Server.SecureCookie}
+	authentication := auth.Auth{
+		DB:           db,
+		SecureCookie: conf.Server.SecureCookie,
+		CrossOrigin:  http.NewCrossOriginProtection(),
+	}
 	messageHandler := api.MessageAPI{Notifier: streamHandler, DB: db}
 	healthHandler := api.HealthAPI{DB: db}
 	clientHandler := api.ClientAPI{