diff --git a/modules/context/api.go b/modules/context/api.go
index 0bf4307726e8..6a9c792370f4 100644
--- a/modules/context/api.go
+++ b/modules/context/api.go
@@ -8,6 +8,8 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/go-macaron/csrf"
+
 	"code.gitea.io/git"
 	"code.gitea.io/gitea/models"
 	"code.gitea.io/gitea/modules/base"
@@ -97,6 +99,17 @@ func (ctx *APIContext) SetLinkHeader(total, pageSize int) {
 	}
 }
 
+// RequireCSRF requires a validated a CSRF token
+func (ctx *APIContext) RequireCSRF() {
+	headerToken := ctx.Req.Header.Get(ctx.csrf.GetHeaderName())
+	formValueToken := ctx.Req.FormValue(ctx.csrf.GetFormName())
+	if len(headerToken) > 0 || len(formValueToken) > 0 {
+		csrf.Validate(ctx.Context.Context, ctx.csrf)
+	} else {
+		ctx.Context.Error(401)
+	}
+}
+
 // APIContexter returns apicontext as macaron middleware
 func APIContexter() macaron.Handler {
 	return func(c *Context) {
diff --git a/public/js/index.js b/public/js/index.js
index fad531cc4991..9bde52f97d1e 100644
--- a/public/js/index.js
+++ b/public/js/index.js
@@ -2590,6 +2590,10 @@ function updateDeadline(deadlineString) {
         data: JSON.stringify({
             'due_date': realDeadline,
         }),
+        headers: {
+            'X-Csrf-Token': csrf,
+            'X-Remote': true,
+        },
         contentType: 'application/json',
         type: 'POST',
         success: function () {
diff --git a/routers/api/v1/api.go b/routers/api/v1/api.go
index 23a85759c2f5..3f0e6c1fb994 100644
--- a/routers/api/v1/api.go
+++ b/routers/api/v1/api.go
@@ -174,11 +174,15 @@ func repoAssignment() macaron.Handler {
 
 // Contexter middleware already checks token for user sign in process.
 func reqToken() macaron.Handler {
-	return func(ctx *context.Context) {
-		if true != ctx.Data["IsApiToken"] {
-			ctx.Error(401)
+	return func(ctx *context.APIContext) {
+		if true == ctx.Data["IsApiToken"] {
+			return
+		}
+		if ctx.IsSigned {
+			ctx.RequireCSRF()
 			return
 		}
+		ctx.Context.Error(401)
 	}
 }