The reason why front-end security is easily overlooked is that many people think that the front-end is just a "display page", and the real important logic and data are on the back-end. However, with the popularity of the front-end separation architecture, the front-end has undertaken more and more data processing and interaction tasks, becoming a potential target of attackers. 1. XSS attacks steal cookies or hijack sessions by injecting malicious scripts to prevent user input, use CSP, and avoid direct insertion of DOM; 2. CSRF attacks induce user operations by forging requests, prevent SameSite cookies, add CSRF tokens, and check Referer headers; 3. The risk of third-party dependency comes from vulnerable npm packages or CDN resources, prevent regular scans of dependencies, avoid unnecessary dependencies, and use SRI verification; 4. Sensitive information is exposed due to debugging hard-coded API keys and other information, prevent front-end writing sensitive information, use .env file management variables, and set permission controls on the back-end. In addition, improving front-end security also requires the use of the security features of modern frameworks, enable HTTPS, minimize exposure, and conduct regular security audits.

Front-end security, simply put, protects the client part of the website or web application to prevent users from being attacked, data stolen or experiences during use. It is not an accessory for backend security, but an indispensable link in the entire security chain.

Why is front-end security easily overlooked?

Many people think that the front-end is just a "display page", and the real logic and data are all in the back-end, but this is not the case. With the popularization of front-end separation architectures, the front-end has undertaken more and more data processing and interaction tasks, which has also made it a potential target for attackers.

Common phenomena include:

• Pages are injected with malicious scripts (XSS)
• User login status stolen (CSRF)
• There are vulnerabilities in third-party dependency libraries
• Sensitive information is exposed to front-end code

These problems often do not appear immediately, but once they break out, they will affect the user experience at the least, and at the worst, they will lead to data leakage or even brand damage.

What are the common front-end security threats?

1. Cross-site scripting attack (XSS)

This is one of the most common front-end attack methods. The attacker injects malicious scripts through input boxes, URL parameters, etc. When other users access the page, the script will be executed, which may steal cookies, hijack the session, or initiate forgery requests.

Precautionary advice:

• Escape all user input (HTML, JS, URL and other scenarios are processed separately)
• Restrict script loading sources using CSP (Content Security Policy)
• Avoid inserting user input directly into the DOM (such as innerHTML )

2. Cross-site request forgery (CSRF)

The attacker induces the user to click a button or picture disguised as a normal link, and thus initiates a request in the name of the user, such as transferring money, modifying passwords and other operations.

Precautionary advice:

• Use SameSite Cookie Attribute
• Add CSRF Token verification mechanism
• Check if the Referer header comes from a trusted source

3. Third-party dependency risk

Now many projects rely on third-party components such as npm packages and CDN resources. If these dependencies have vulnerabilities, they are easily exploited.

Precautionary advice:

• Security issues for periodic scanning of dependencies (such as using Snyk, Dependabot)
• Try to avoid introducing unnecessary dependencies
• Verify CDN resource integrity using Subresource Integrity (SRI)

4. Sensitive information exposure

Sometimes, for the convenience of debugging, sensitive information such as API keys, internal paths, environment variables, etc. are hardcoded in the front-end code, which is easy to be reversely analyzed.

Precautionary advice:

• Don't write sensitive information into front-end code
• Use .env files to manage environment variables and make sure they are not packaged during build
• The backend should set permission control to avoid the frontend being able to directly access the high-permission interface.

How to improve the overall security of front-end projects?

In addition to protecting specific attack types, you can also make some optimizations from the development process and project structure:

• Security features using modern frameworks
  Mainstream frameworks such as Vue, React, and Angular themselves provide some security mechanisms, such as automatic escape, template binding, etc., and make good use of them.

• Enable HTTPS
  All front-end resources should be transmitted over HTTPS to prevent the middleman from tampering with the page content or injecting malicious code.

• Minimize front-end exposure
  Unnecessary functional modules, debugging tools, and error stack information should all be closed in the production environment.

• Regular security audits
  You can use Lighthouse, OWASP ZAP and other tools to automatically detect potential risks in a timely manner.

Overall, front-end security is not particularly complicated, but it is easily overlooked. As long as you pay more attention to the development process, many problems can be avoided in advance. Basically that's it, don't wait until something happens to remember to remedy it.

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