CORS configuration in Security in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the effect of this Spring Security CORS configuration?

Consider this Spring Security configuration snippet for CORS:

http.cors().and().csrf().disable();

What does this configuration do regarding CORS requests?

Spring Boot

http.cors().and().csrf().disable();

A Enables CORS with custom settings but keeps CSRF enabled.

B Disables CORS support and enables CSRF protection.

C Disables both CORS and CSRF protections.

D Enables CORS support using default settings and disables CSRF protection.

💡 Hint

Think about what calling cors() and csrf().disable() does in Spring Security.

Calling http.cors() enables CORS support with default configuration. Calling csrf().disable() disables CSRF protection. So this configuration enables CORS and disables CSRF.

📝 Syntax

intermediate

Which option correctly defines a CORS configuration source bean in Spring Boot?

You want to define a bean that customizes CORS mappings in Spring Boot Security. Which code snippet is syntactically correct?

A public CorsConfigurationSource corsConfigurationSource() { CorsConfiguration config = new CorsConfiguration(); config.addAllowedOrigin("*"); UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource(); source.registerCorsConfiguration("/**", config); return source; }

B @Bean public void corsConfigurationSource() { CorsConfiguration config = new CorsConfiguration(); config.addAllowedOrigin("*"); UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource(); source.registerCorsConfiguration("/**", config); }

C @Bean public CorsConfigurationSource corsConfigurationSource() { CorsConfiguration config = new CorsConfiguration(); config.addAllowedOrigin("*"); UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource(); source.registerCorsConfiguration("/**", config); return source; }

D @Bean CorsConfigurationSource corsConfigurationSource() { CorsConfiguration config = new CorsConfiguration(); config.addAllowedOrigin("*"); UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource(); source.registerCorsConfiguration("/**", config); return source; }

💡 Hint

Remember the @Bean annotation and method return type are required for Spring to recognize the bean.

Option C correctly uses @Bean annotation, returns CorsConfigurationSource, and returns the source object. Option C misses @Bean, B returns void, D misses public modifier (optional but recommended).

🔧 Debug

advanced

Why does this CORS configuration not allow requests from 'http://example.com'?

Given this CORS configuration bean:

@Bean
public CorsConfigurationSource corsConfigurationSource() {
  CorsConfiguration config = new CorsConfiguration();
  config.addAllowedOrigin("http://example.com");
  config.addAllowedMethod("GET");
  UrlBasedCorsConfigurationSource source = new UrlBasedCorsConfigurationSource();
  source.registerCorsConfiguration("/**", config);
  return source;
}

And the security config:

http.cors().and().csrf().disable();

Why might requests from 'http://example.com' still be blocked by the browser?

A The allowed origin must be set with a trailing slash like 'http://example.com/'.

B The allowed origin must be set using 'setAllowedOriginPatterns' instead of 'addAllowedOrigin' to support subdomains or patterns.

C The CORS configuration bean is not registered because the method lacks the @Configuration annotation.

D CSRF is disabled, so CORS requests are blocked by default.

💡 Hint

Think about how Spring Security matches origins with patterns.

Spring Security 5.3+ recommends using setAllowedOriginPatterns to allow flexible origins like subdomains or wildcard patterns. addAllowedOrigin matches exact origins only. If the request origin differs slightly, it will be blocked.

❓ state_output

advanced

What is the value of 'allowedMethods' after this CORS config code runs?

Given this code snippet:

CorsConfiguration config = new CorsConfiguration();
config.addAllowedMethod("GET");
config.addAllowedMethod("POST");
config.setAllowedMethods(List.of("PUT", "DELETE"));
List allowedMethods = config.getAllowedMethods();

What is the content of 'allowedMethods'?

A ["PUT", "DELETE"]

B ["GET", "POST", "PUT", "DELETE"]

C ["GET", "POST"]

D null

💡 Hint

Consider what setAllowedMethods does compared to addAllowedMethod.

setAllowedMethods replaces the entire list of allowed methods, so the previous addAllowedMethod calls are overwritten. The final list contains only PUT and DELETE.

🧠 Conceptual

expert

Which statement best describes the role of CORS configuration in Spring Security?

Select the most accurate description of how CORS configuration interacts with Spring Security and browser behavior.

A CORS configuration in Spring Security controls which cross-origin requests the server accepts, but browsers enforce CORS policies based on server response headers.

B CORS configuration in Spring Security automatically adds Access-Control-Allow-Origin: * header to all responses.

C CORS configuration in Spring Security only affects CSRF tokens and does not influence cross-origin requests.

D CORS configuration in Spring Security disables browser CORS checks entirely, allowing all cross-origin requests.

💡 Hint

Think about the difference between server-side configuration and browser enforcement.

Spring Security's CORS configuration sets headers that tell browsers which cross-origin requests are allowed. Browsers enforce CORS by blocking disallowed requests. The server does not disable browser checks but provides headers to guide them.