diff --git a/manifest.json b/manifest.json
index 89a62be7..3d4d3f08 100644
--- a/manifest.json
+++ b/manifest.json
@@ -38,6 +38,7 @@
       "vendor/semver-bundle/semver.js",
       "vendor/db-to-cloud/db-to-cloud.min.js",
       "vendor/uuid/uuid.min.js",
+      "vendor/webext-launch-web-auth-flow/webext-launch-web-auth-flow.js",
       "background/token-manager.js",
       "background/sync.js",
       "background/content-scripts.js",
diff --git a/tools/build-vendor.js b/tools/build-vendor.js
index 1e3d5c24..73197098 100644
--- a/tools/build-vendor.js
+++ b/tools/build-vendor.js
@@ -62,6 +62,9 @@ const files = {
   ],
   'uuid': [
     'dist/umd/uuidv4.min.js → uuid.min.js'
+  ],
+  'webext-launch-web-auth-flow': [
+    'dist/webext-launch-web-auth-flow.js → webext-launch-web-auth-flow.js'
   ]
 };
 
diff --git a/vendor/webext-launch-web-auth-flow/LICENSE b/vendor/webext-launch-web-auth-flow/LICENSE
new file mode 100644
index 00000000..792e1731
--- /dev/null
+++ b/vendor/webext-launch-web-auth-flow/LICENSE
@@ -0,0 +1,22 @@
+The MIT License (MIT)
+
+Copyright (c) 2020 eight
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+
diff --git a/vendor/webext-launch-web-auth-flow/README.md b/vendor/webext-launch-web-auth-flow/README.md
new file mode 100644
index 00000000..e399613d
--- /dev/null
+++ b/vendor/webext-launch-web-auth-flow/README.md
@@ -0,0 +1,5 @@
+## webext-launch-web-auth-flow v0.0.0
+
+Following files are copied from npm (node_modules):
+
+* webext-launch-web-auth-flow.js: dist\webext-launch-web-auth-flow.js
diff --git a/vendor/webext-launch-web-auth-flow/webext-launch-web-auth-flow.js b/vendor/webext-launch-web-auth-flow/webext-launch-web-auth-flow.js
new file mode 100644
index 00000000..243bb83d
--- /dev/null
+++ b/vendor/webext-launch-web-auth-flow/webext-launch-web-auth-flow.js
@@ -0,0 +1,185 @@
+var webextLaunchWebAuthFlow = (function () {
+  'use strict';
+
+  function asyncGeneratorStep(gen, resolve, reject, _next, _throw, key, arg) {
+    try {
+      var info = gen[key](arg);
+      var value = info.value;
+    } catch (error) {
+      reject(error);
+      return;
+    }
+
+    if (info.done) {
+      resolve(value);
+    } else {
+      Promise.resolve(value).then(_next, _throw);
+    }
+  }
+
+  function _asyncToGenerator(fn) {
+    return function () {
+      var self = this,
+          args = arguments;
+      return new Promise(function (resolve, reject) {
+        var gen = fn.apply(self, args);
+
+        function _next(value) {
+          asyncGeneratorStep(gen, resolve, reject, _next, _throw, "next", value);
+        }
+
+        function _throw(err) {
+          asyncGeneratorStep(gen, resolve, reject, _next, _throw, "throw", err);
+        }
+
+        _next(undefined);
+      });
+    };
+  }
+
+  /* eslint-env webextensions */
+  function createWindow(_x) {
+    return _createWindow.apply(this, arguments);
+  }
+
+  function _createWindow() {
+    _createWindow = _asyncToGenerator(function* (options) {
+      if (browser.windows) {
+        return yield browser.windows.create(options);
+      }
+
+      const tabOptions = {
+        active: options.focused,
+        url: options.url
+      };
+      const tab = yield browser.tabs.create(tabOptions);
+      return {
+        tabs: [tab]
+      };
+    });
+    return _createWindow.apply(this, arguments);
+  }
+
+  function updateWindow(_x2, _x3, _x4) {
+    return _updateWindow.apply(this, arguments);
+  }
+
+  function _updateWindow() {
+    _updateWindow = _asyncToGenerator(function* (windowId, tabId, options) {
+      if (windowId) {
+        return yield browser.windows.update(windowId, options);
+      }
+
+      return yield browser.tabs.update(tabId, {
+        active: options.focused
+      });
+    });
+    return _updateWindow.apply(this, arguments);
+  }
+
+  function closeWindow(_x5, _x6) {
+    return _closeWindow.apply(this, arguments);
+  }
+
+  function _closeWindow() {
+    _closeWindow = _asyncToGenerator(function* (windowId, tabId) {
+      if (windowId) {
+        return yield browser.windows.remove(windowId);
+      }
+
+      return yield browser.tabs.remove(tabId);
+    });
+    return _closeWindow.apply(this, arguments);
+  }
+
+  function defer() {
+    const o = {};
+    o.promise = new Promise((resolve, reject) => {
+      o.resolve = resolve;
+      o.reject = reject;
+    });
+    return o;
+  }
+
+  function launchWebAuthFlow(_x7) {
+    return _launchWebAuthFlow.apply(this, arguments);
+  }
+
+  function _launchWebAuthFlow() {
+    _launchWebAuthFlow = _asyncToGenerator(function* ({
+      url,
+      redirect_uri,
+      interactive = false
+    }) {
+      const wInfo = yield createWindow({
+        // Firefox doesn't support focused
+        type: "popup",
+        url,
+        state: "minimized"
+      });
+      const windowId = wInfo.id;
+      const tabId = wInfo.tabs[0].id;
+
+      const _defer = defer(),
+            promise = _defer.promise,
+            resolve = _defer.resolve,
+            reject = _defer.reject;
+
+      browser.webRequest.onBeforeRequest.addListener(onBeforeRequest, {
+        urls: ["*://*/*"],
+        tabId,
+        types: ["main_frame"]
+      }, ["blocking"]);
+      browser.webNavigation.onDOMContentLoaded.addListener(onDOMContentLoaded);
+      browser.tabs.onRemoved.addListener(onTabRemoved);
+
+      try {
+        return yield promise;
+      } finally {
+        cleanup();
+      }
+
+      function onBeforeRequest(details) {
+        if (details.frameId || details.tabId !== tabId) return;
+        if (!details.url.startsWith(redirect_uri)) return;
+        resolve(details.url);
+        return {
+          cancel: true
+        };
+      }
+
+      function onDOMContentLoaded(details) {
+        if (details.frameId || details.tabId !== tabId) return;
+
+        if (interactive) {
+          updateWindow(windowId, tabId, {
+            focused: true,
+            state: "normal"
+          }).catch(err => console.error(err));
+        } else {
+          reject(new Error("User interaction required"));
+        }
+
+        browser.webNavigation.onDOMContentLoaded.removeListener(onDOMContentLoaded);
+      }
+
+      function onTabRemoved(removedTabId) {
+        if (removedTabId === tabId) {
+          reject(new Error("Canceled by user"));
+        }
+      }
+
+      function cleanup() {
+        browser.webRequest.onBeforeRequest.removeListener(onBeforeRequest);
+        browser.webNavigation.onDOMContentLoaded.removeListener(onDOMContentLoaded);
+        browser.tabs.onRemoved.removeListener(onTabRemoved);
+        closeWindow(windowId, tabId).catch(err => console.error(err));
+      }
+    });
+    return _launchWebAuthFlow.apply(this, arguments);
+  }
+
+  return launchWebAuthFlow;
+
+}());
+//# sourceMappingURL=webext-launch-web-auth-flow.js.map