Facebook最近在处理会话重定向的方式上做出了改变。有关公告，请参阅本周Operation Developer Love博客文章中的“会话重定向行为的更改”。

使用angular和angular ui router，你可以修复这个问题

    app.config(function ($stateProvider, $urlRouterProvider, $locationProvider) {

      // Make a trailing slash optional for all routes
      // - Note: You'll need to specify all urls with a trailing slash if you use this method.
      $urlRouterProvider.rule(function ($injector, $location) {
        /***
        Angular misbehaves when the URL contains a "#_=_" hash.

        From Facebook:
          Change in Session Redirect Behavior
          This week, we started adding a fragment #_=_ to the redirect_uri when this field is left blank.
          Please ensure that your app can handle this behavior.

        Fix:
          http://stackoverflow.com/questions/7131909/facebook-callback-appends-to-return-url#answer-7297873
        ***/
        if ($location.hash() === '_=_'){
          $location.hash(null);
        }

        var path = $location.url();

        // check to see if the path already has a slash where it should be
        if (path[path.length - 1] === '/' || path.indexOf('/?') > -1) {
          return;
        }
        else if (path.indexOf('?') > -1) {
          $location.replace().path(path.replace('?', '/?'));
        }
        else {
          $location.replace().path(path + '/');
        }
      });

      // etc ...
    });
});

如果你使用的是带有hashbang (/#!/) url的JS框架，比如Angular，这可能会成为一个严重的问题。实际上，Angular会认为带有非hashbang片段的url是无效的，并抛出一个错误:

Error: Invalid url "http://example.com/#_=_", missing hash prefix "#!".

如果你在这种情况下(重定向到你的域根目录)，不要这样做:

window.location.hash = ''; // goes to /#, which is no better

简单地做:

window.location.hash = '!'; // goes to /#!, which allows Angular to take care of the rest

使用Angular 2 (RC5)和基于哈希的路由，我这样做:

const appRoutes: Routes = [
  ...
  {path: '_', redirectTo: '/facebookLoginSuccess'},
  ...
]

and

export const routing = RouterModule.forRoot(appRoutes, { useHash: true });

据我所知，路由中的=字符被解释为可选路由参数定义的一部分(见https://angular.io/docs/ts/latest/guide/router.html#!#optional-route-parameters)，因此不涉及路由匹配。

不知道他们为什么这样做，但是，你可以通过重置页面顶部的哈希来解决这个问题:

if (window.location.hash == "#_=_")
  window.location.hash = "";

适用于PHP SDK用户

我只是通过在转发之前删除额外的部分来解决这个问题。

 $loginURL = $helper->getLoginUrl($redirectURL, $fbPermissions);
 $loginURL = str_replace("#_=_", "", $loginURL);
 header("Location: " . $loginURL);