Laravel 使得防止应用 遭到跨站请求伪造攻击变得简单。 Laravel 自动为每一个被应用管理的有效用户会话生成一个 CSRF “令牌”，该令牌用于验证授权用 户和发起请求者是否是同一个人。 任何时候在 Laravel 应用中定义 HTML 表单，都需要在表单中引入 CSRF 令牌字段，这样 CSRF 保护中间件才能够正常验证请求。想要生成包含 CSRF 令牌的隐藏输入字段，可以使用辅助函 数 csrf_field 来实现：
中间件组 web 中的中间件 VerifyCsrfToken 会自动为我们验证请求输入的 token 值和 Session 中存储的 token 是否一致。
<form method="POST" action="/profile"> {{ csrf_field() }}
...
</form>
跨站请求伪造(Cross-Site Request Forgery, CSRF)，恶意网站通过脚本向当前用户浏览器打开的其它页面的 URL 发起恶意请求，由于同一浏览器进程下 Cookie 可见性，导致用户身份被盗用，完成恶意网站脚本中指定的操作。
漏洞危害
- 信息泄露：如登录ID，隐私信息等。
- 恶意操作：如加好友，加购物车，删除数据等。
开放平台文档中心 https://docs.open.alipay.com/399/106918/
Cross Site Request Forgery protection | Django documentation | Django https://docs.djangoproject.com/en/3.0/ref/csrf/
Cross Site Request Forgery protection¶
The CSRF middleware and template tag provides easy-to-use protection against Cross Site Request Forgeries. This type of attack occurs when a malicious website contains a link, a form button or some JavaScript that is intended to perform some action on your website, using the credentials of a logged-in user who visits the malicious site in their browser. A related type of attack, ‘login CSRF’, where an attacking site tricks a user’s browser into logging into a site with someone else’s credentials, is also covered.
The first defense against CSRF attacks is to ensure that GET requests (and other ‘safe’ methods, as defined by RFC 7231#section-4.2.1) are side effect free. Requests via ‘unsafe’ methods, such as POST, PUT, and DELETE, can then be protected by following the steps below.
Why might a user encounter a CSRF validation failure after logging in?¶
For security reasons, CSRF tokens are rotated each time a user logs in. Any page with a form generated before a login will have an old, invalid CSRF token and need to be reloaded. This might happen if a user uses the back button after a login or if they log in a different browser tab.