diff --git a/Changelog.md b/Changelog.md
index 8735c31ee..d867286af 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -12,6 +12,7 @@
 * Indicate proper way to report bugs in the sidebar [#7039](https://github.com/diaspora/diaspora/pull/7039)
 * Remove text color from notification mails and fix sender avatar [#7054](https://github.com/diaspora/diaspora/pull/7054)
 * Make the session cookies HttpOnly again [#7041](https://github.com/diaspora/diaspora/pull/7041)
+* Invalidate sessions with invalid CSRF tokens [#7050](https://github.com/diaspora/diaspora/pull/7050)
 
 ## Bug fixes
 * Post comments no longer get collapsed when interacting with a post [#7040](https://github.com/diaspora/diaspora/pull/7040)
diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index ebd5b0343..bc79acdb2 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -5,7 +5,17 @@
 class ApplicationController < ActionController::Base
   before_action :force_tablet_html
   has_mobile_fu
-  protect_from_forgery except: :receive
+  protect_from_forgery except: :receive, with: :exception
+
+  rescue_from ActionController::InvalidAuthenticityToken do
+    if user_signed_in?
+      logger.warn "#{current_user.diaspora_handle} CSRF token fail. referer: #{request.referer || 'empty'}"
+      Workers::Mail::CsrfTokenFail.perform_async(current_user.id)
+      sign_out current_user
+    end
+    flash[:error] = I18n.t("error_messages.csrf_token_fail")
+    redirect_to new_user_session_path format: request[:format]
+  end
 
   before_action :ensure_http_referer_is_set
   before_action :set_locale
diff --git a/app/mailers/notification_mailers/csrf_token_fail.rb b/app/mailers/notification_mailers/csrf_token_fail.rb
new file mode 100644
index 000000000..435f9d87b
--- /dev/null
+++ b/app/mailers/notification_mailers/csrf_token_fail.rb
@@ -0,0 +1,7 @@
+module NotificationMailers
+  class CsrfTokenFail < NotificationMailers::Base
+    def set_headers
+      @headers[:subject] = I18n.t("notifier.csrf_token_fail.subject", name: @recipient.name)
+    end
+  end
+end
diff --git a/app/mailers/notifier.rb b/app/mailers/notifier.rb
index e92795a18..80630ebe2 100644
--- a/app/mailers/notifier.rb
+++ b/app/mailers/notifier.rb
@@ -87,6 +87,10 @@ class Notifier < ActionMailer::Base
     send_notification(:confirm_email, recipient_id)
   end
 
+  def csrf_token_fail(recipient_id)
+    send_notification(:csrf_token_fail, recipient_id)
+  end
+
   private
   def send_notification(type, *args)
     @notification = NotificationMailers.const_get(type.to_s.camelize).new(*args)
diff --git a/app/views/notifier/csrf_token_fail.markerb b/app/views/notifier/csrf_token_fail.markerb
new file mode 100644
index 000000000..22f3164ea
--- /dev/null
+++ b/app/views/notifier/csrf_token_fail.markerb
@@ -0,0 +1 @@
+<%= t("notifier.csrf_token_fail.body", name: @notification.recipient_first_name, link: "https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)") %>
diff --git a/app/workers/mail/csrf_token_fail.rb b/app/workers/mail/csrf_token_fail.rb
new file mode 100644
index 000000000..a3372b322
--- /dev/null
+++ b/app/workers/mail/csrf_token_fail.rb
@@ -0,0 +1,11 @@
+module Workers
+  module Mail
+    class CsrfTokenFail < Base
+      sidekiq_options queue: :low
+
+      def perform(user_id)
+        Notifier.csrf_token_fail(user_id).deliver_now
+      end
+    end
+  end
+end
diff --git a/config/locales/diaspora/en.yml b/config/locales/diaspora/en.yml
index 8d952a298..62d697149 100644
--- a/config/locales/diaspora/en.yml
+++ b/config/locales/diaspora/en.yml
@@ -75,6 +75,7 @@ en:
     helper:
       correct_the_following_errors_and_try_again: "Correct the following errors and try again."
     need_javascript: "This website requires JavaScript to function properly. If you disabled JavaScript, please enable it and refresh this page."
+    csrf_token_fail: "The CSRF token is invalid. Please sign in and try again."
 
   admins:
     admin_bar:
@@ -695,6 +696,18 @@ en:
     confirm_email:
         subject: "Please activate your new email address %{unconfirmed_email}"
         click_link: "To activate your new email address %{unconfirmed_email}, please follow this link:"
+    csrf_token_fail:
+      subject: "We received an unauthorized request from your account, %{name}"
+      body: |-
+        Hello %{name},
+
+        We received a request with a wrong/missing CSRF token from your account. To prevent any possible damage you have been logged out.
+
+        For more information on CSRF see [%{link}](%{link}).
+
+        Sorry,
+
+        The diaspora* email robot!
     report_email:
         type:
           post: "post"
diff --git a/spec/integration/application_spec.rb b/spec/integration/application_spec.rb
new file mode 100644
index 000000000..7f5527896
--- /dev/null
+++ b/spec/integration/application_spec.rb
@@ -0,0 +1,54 @@
+require "spec_helper"
+
+describe ApplicationController, type: :request do
+  describe "csrf token validation" do
+    context "without a current user" do
+      before do
+        @user = alice
+        @user.password = "evankorth"
+        @user.password_confirmation = "evankorth"
+        @user.save
+      end
+
+      it "redirects to the new session page on validation fails" do
+        expect_any_instance_of(SessionsController).to receive(:verified_request?).and_return(false)
+        post "/users/sign_in", user: {remember_me: 0, username: @user.username, password: "evankorth"}
+        expect(response).to redirect_to new_user_session_path
+        expect(flash[:error]).to eq(I18n.t("error_messages.csrf_token_fail"))
+      end
+
+      it "doesn't redirect to the new session page if the validation succeeded" do
+        expect_any_instance_of(SessionsController).to receive(:verified_request?).and_return(true)
+        post "/users/sign_in", user: {remember_me: 0, username: @user.username, password: "evankorth"}
+        expect(response).to redirect_to stream_path
+        expect(flash[:error]).to be_blank
+      end
+    end
+
+    context "with a current user" do
+      before do
+        sign_in alice
+      end
+
+      it "signs out users if a wrong token was given" do
+        expect_any_instance_of(UsersController).to receive(:verified_request?).and_return(false)
+        put edit_user_path, user: {language: "en"}
+        expect(response).to redirect_to new_user_session_path
+        expect(flash[:error]).to eq(I18n.t("error_messages.csrf_token_fail"))
+      end
+
+      it "sends an email to the current user if the token validation failed" do
+        expect_any_instance_of(UsersController).to receive(:verified_request?).and_return(false)
+        expect(Workers::Mail::CsrfTokenFail).to receive(:perform_async).with(alice.id)
+        put edit_user_path, user: {language: "en"}
+      end
+
+      it "doesn't sign out users if the token was correct" do
+        expect_any_instance_of(UsersController).to receive(:verified_request?).and_return(true)
+        put edit_user_path, user: {language: "en"}
+        expect(response).not_to be_redirect
+        expect(flash[:error]).to be_blank
+      end
+    end
+  end
+end
diff --git a/spec/mailers/notifier_spec.rb b/spec/mailers/notifier_spec.rb
index 61595a7eb..3669fddd9 100644
--- a/spec/mailers/notifier_spec.rb
+++ b/spec/mailers/notifier_spec.rb
@@ -432,6 +432,26 @@ describe Notifier, type: :mailer do
     end
   end
 
+  describe ".csrf_token_fail" do
+    let(:email) { Notifier.csrf_token_fail(alice.id) }
+
+    it "goes to the right person" do
+      expect(email.to).to eq([alice.email])
+    end
+
+    it "has the correct subject" do
+      expect(email.subject).to eq(I18n.translate("notifier.csrf_token_fail.subject", name: alice.name))
+    end
+
+    it "has the receivers name in the body" do
+      expect(email.body.encoded).to include(alice.person.profile.first_name)
+    end
+
+    it "has some informative text in the body" do
+      expect(email.body.encoded).to include("https://www.owasp.org/index.php/Cross-Site_Request_Forgery_(CSRF)")
+    end
+  end
+
   describe "hashtags" do
     it "escapes hashtags" do
       mails = Notifier.admin("#Welcome to bureaucracy!", [bob])
diff --git a/spec/workers/mail/csrf_token_fail_spec.rb b/spec/workers/mail/csrf_token_fail_spec.rb
new file mode 100644
index 000000000..321b06dc4
--- /dev/null
+++ b/spec/workers/mail/csrf_token_fail_spec.rb
@@ -0,0 +1,18 @@
+#   Copyright (c) 2010-2011, Diaspora Inc.  This file is
+#   licensed under the Affero General Public License version 3 or later.  See
+#   the COPYRIGHT file.
+
+require "spec_helper"
+
+describe Workers::Mail::CsrfTokenFail do
+  describe "#perfom" do
+    it "should call .deliver on the notifier object" do
+      user = alice
+      mail_double = double
+      expect(mail_double).to receive(:deliver_now)
+      expect(Notifier).to receive(:csrf_token_fail).with(user.id).and_return(mail_double)
+
+      Workers::Mail::CsrfTokenFail.new.perform(user.id)
+    end
+  end
+end