How CORS errors affect web security and developer experience

Highlights

You’ll learn how CORS error affects web security and developer experience

Impact on web security and developer experience:

• It weakens API protection when configured wrongly

• Increases development time as debugging is time-consuming
• It complicates cross-origin requests, leading to development delays

Practical solutions:

• Configure CORS headers properly

• Handle credentials securely by using HTTPS and authentication mechanisms

Set up the right mechanism to manage CORS and prevent web security risks. Opt for a compliant CMS today. Talk to us to get started.

 

Keep reading to learn more!

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CORS is a feature built into browsers for extra security. It prevents random websites from using your cookies to send an API request to other websites. When wrongly configured, it creates a problem that developers have become familiar with—CORS error.

Aside from the security issues, CORS errors take time to debug. Even when they work well, they may block legitimate requests if the settings are too strict. That impacts user and developer experience. We explore how that happens and best practices to help developers manage CORS issues.

 

 

CORS errors and web security

CORS prevents malicious cross-origin attacks, such as cross-site request forgery (CSRF). By enforcing strict domain policies, it blocks requests to APIs or data from malicious websites. CORS errors occur as a result of improper CORS configuration, creating all sorts of problems that impact web security. 

Impact of CORS errors on web applications

A CORS error restricts web application requests to external domains for resources. Although CORS improves security, it can also disrupt legitimate data sharing if not properly configured. CORS errors disrupt cross-origin API calls and the user experience, among others.

Wrong CORS configurations create vulnerabilities that attackers can exploit to launch cross-site scripting (XSS) and request forgery attacks. It also creates extra workload for developers because it takes time to fix.

Potential risks of improper CORS implementation

Aside from the obvious security issues mentioned, here are other potential risks of improper CORS handling.

• Compromised application integrity and user trust.
• Reduced control over data privacy
• Exposure to credential theft.
• Unintended data sharing with malicious sites.
• Bypass of same-origin policy restrictions.

Best practices for secure CORS policy enforcement

Considering the security implications and potential risks of misconfigured CORS, developers must create CORS policies to diagnose and troubleshoot CORS errors. There are also other proactive actions they can take, as follows:

• Whitelist specific domains that are permitted to access resources.
• Use HTTP methods that support cross-origin requests.
• Validate user inputs to prevent injection attacks.
• Review and update CORS policies regularly to address new security threats.

The role of HTTP headers in CORS

Servers manage CORS using HTTP headers to communicate permissions to web browsers. Here are three important HTTP headers and their roles in CORS.

• Access-Control-Allow-Origin header: This header lists the origins that allow access to data. It defines the domains that can communicate with the server, preventing unauthorized access.

• Access-Control-Allow-Credentials header: Servers use this header to allow browsers to share credentials along with requests. When it is not properly configured, it blocks requests that come with credentials.

• Access-Control-Allow-Methods header: This header defines allowed HTTP methods—these methods are then granted permission to make cross-origin requests.

CORS preflight requests

A preflight request is a request before the main request. It confirms whether the target server is prepared to handle the main request. If the target server cannot handle the request, you get an error. Here are common preflight request errors and how to deal with them.

• No Access-Control-Allow-Origin Header: This common preflight request error requires that you include the No Access-Control-Allow-Origin header.

• Forbidden Method Disallowed Request Method: This error means that you are using a blocked HTTP method. You must edit your server settings to include the correct methods.

Common CORS issues and how to fix them

Fixing a CORS error depends on its nature. Therefore, it is essential to assess the error message before taking action. Here are common CORS errors.

• Missing Access-Control-Allow-Origin Header: This error occurs when a request comes in, and the server response has no header that specifies permitted origins.

• Credentials handling issues: Credential handling errors happen when a browser receives a request with credentials for a misconfigured Access-Control-Allow-Credentials header.

• Preflight request failures: When an options request is sent before the main request, it has to have the right HTTP methods and headers. When those are absent, the server rejects the request, which means the main request will not be permitted.

How to fix CORS errors

To fix CORS errors, you need to first understand the error message. 

• Identify the source of the error: Use developer tools or check the browser console to see the error message and where it is coming from.
• Configure allowed origins: To configure allowed origins, set the Access-Control-Allow-Origin header to specify the domains you permit to make requests.
• Set allowed methods: Include the necessary HTTP methods in the Access-Control-Allow-Methods header.
• Properly handle credentials: To manage credentials, use the Access-Control-Allow-Credentials header for requests.
• Test the configuration: Check the browsers and test multiple scenarios to ensure you applied the right solutions across the board.

CORS in API development

APIs use headers to control access for CORS. You must set allowed origins, specify permitted HTTP methods, and acceptable request headers. You may also define preflight cache duration—the response headers clients see, and if credentials are allowed.

To protect your web application against cross-origin threats, you should:

• Use HTTPS for better security.
• Limit the requests a client can make to your API within a certain time frame.
• Monitor your API regularly to respond to threats.

Case study

MoneyHero Group

MoneyHero needed a secure solution to ease developer experience, and Contentstack’s headless CMS offered the solution.

Its robust security and serverless function support eased developer experience and enabled the organization to improve product rollout time by 85%.

Hear from Andrew de Ridder, the Head of Application Engineering. “The technical tooling and APIs that Contentstack provides allows our engineering teams the power and flexibility to surface content wherever it's needed, from multiple websites in different regions, to email, social media, or whatever use case comes next.”

Read more about how MoneyHero delivered content agility through Contentstack’s industry-leading headless CMS.

Welcome Tech

WelcomeTech went from struggling with security to implementing Contentstack’s headless CMS with serverless functions for CORS handling. It addressed their security challenges and improved productivity by 50%.

Hear from William Leborgne, the Director of Content. “I’ve looked at more than half a dozen CMSes, and Contentstack came to the top for all the right reasons. The product is incredibly user-friendly. The support team was excellent. The integration with our system was seamless. The engineering team is delighted. Integrations for personalization, AB testing, and all the other bells and whistles are there in spades, so it’s a no-brainer.”

Read more about how Welcome Tech boosted productivity with Contentstack’s CMS.

FAQ section

What causes a CORS error?

Blocked requests cause CORS error after a web application requests resources from another origin.

How can I fix a CORS error in my application?

Depending on the different errors we have explored, fixing a CORS error involves dealing with the problem triggering the error.

What are the security risks associated with CORS?

Wrong CORS configurations can lead to XSS and CSRF attacks, as well as expose data and web applications to unauthorized access.

What are the key HTTP headers involved in CORS?

The key CORS headers are Access-Control-Allow-Origin, Access-Control-Allow-Methods, and (optional) Access-Control-Allow-Headers.

Learn more

CORS is an important part of website security because it dictates how systems share resources. If CORS is not properly implemented, errors will affect web security, functionality and user experience.

Knowing how to address CORS errors allows you to maintain data integrity and web security. Contentstack’s headless CMS manages these issues behind the scenes, with adequate security to keep you safe. Talk to us today for your secure CMS solution.