Front-end security vulnerabilities need to be taken seriously. XSS prevention measures include input escape, using CSP, avoiding inline script operations, and setting cookie attributes; CSRF response methods include SameSite attribute, anti-CSRF token, and POST requests; third-party libraries need to regularly check and update, use audit tools, and avoid unknown plug-ins; other issues such as enabling HTTPS, not exposing sensitive information, reasonable caching, and preventing click hijacking must also be paid attention to.
Front-end security vulnerabilities are actually not far from us, especially now that web page functions are becoming more and more complex and user interactions are becoming more and more. Many people think that the front-end is just displaying content, but in fact, many attacks start from here. Therefore, during the development process, we must consider some common safety hazards in advance and take corresponding protective measures.

How to prevent XSS (cross-site scripting attack)?
XSS is one of the most common front-end security issues. The attacker injects malicious scripts into the page and executes them when other users browse, thereby stealing cookies, hijacking sessions, or launching phishing attacks.
There are several key points to prevent XSS:

- Escape user input : HTML escapes before displaying whether the user enters comments, usernames, or form content.
- Using Content Security Policy (CSP) : This is an HTTP response header that can limit which resources can be loaded and executed, effectively preventing inline script execution.
- Avoid innerHTML or dangerouslySetInnerHTML : This type of operation is prone to introducing malicious code, try to use a safer method to update the DOM.
- Set the HttpOnly and Secure properties of the cookie : This way, even if it is injected into the script, the cookie cannot be read.
Now many frameworks such as React have done partial defenses by default, but they cannot rely entirely on the framework, so understanding the principles is more important.
How to deal with CSRF (cross-site request forgery)?
The core of CSRF is that the attacker induces the user to access a malicious website, and then uses the user's login status to initiate requests that are not intended, such as transferring money, modifying information, etc.

Although CSRF is more of a problem that the backend needs to deal with, the frontend can also cooperate to make some prevention:
- Use SameSite Cookie Properties : Set to
Strict
orLax
can prevent cross-site requests from carrying cookies. - Add anti-CSRF token : It is usually generated by the backend. The frontend brings this token in each sensitive request, and then processes the request after verification.
- Use POST requests instead of GET requests to make state changes : GET requests are more likely to be forged, and POST requires at least a certain triggering condition.
Especially for some operations that require identity authentication, the front and back ends cooperate to do a good job in the Token verification mechanism, which can greatly reduce risks.
Unsafe third-party libraries can also bring risks
Almost all kinds of third-party libraries are used in front-end projects, such as jQuery, React, Vue, etc. But if you use outdated or have known vulnerabilities, it may become an attack portal.
The solution is actually very direct:
- Regularly check for dependencies for security updates
- Use tools like
npm audit
to scan for vulnerabilities - Avoid introducing unnecessary or unknown plugins
- For large projects, consider using dependency management tools such as Dependabot to automatically upgrade
Sometimes when a small module has problems, the entire application may be affected. Therefore, the library selection cannot only look at the functions, but also the maintenance status and community feedback.
Other common problems cannot be ignored
In addition to the above main issues, there are some details that are easily overlooked:
- HTTPS must be enabled : data transmitted in plain text is easily intercepted by the middleman.
- Do not expose sensitive information on the front end : such as API keys, database structures, etc., these should be controlled in the backend.
- Set caching policies reasonably : Some pages or data should not be cached by the browser, otherwise they may be obtained by others.
- Clickjacking : You can use X-Frame-Options or CSP to limit whether the page is allowed to be nested.
These problems seem small, but if something happens, it will have a great impact. Especially in enterprise-level applications, security is often not "icing on the cake", but a "bottom line requirement".
Basically that's it. Front-end security seems complicated, but in fact, many of them are basic skills. The key is to consciously pay attention to these points in daily development and don’t wait until they are launched before remediation.
The above is the detailed content of Frontend Security Vulnerabilities and Prevention. For more information, please follow other related articles on the PHP Chinese website!

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