The same-origin policy restricts web pages from making requests to a different domain, which improves security.
However, this can limit legitimate use cases such as API access across subdomains.
Cross-Origin Resource Sharing (CORS) allows servers to define an access control policy using HTTP headers to enable cross-origin requests.
The “Access-Control-Allow-Origin” header indicates which domains are permitted to access a resource, but it does not support listing multiple origins directly.
This article explores secure and practical methods to allow multiple origin domains using .htaccess configurations, focusing on Apache servers.
It covers implementation strategies, best practices, and common pitfalls and provides examples of secure techniques using regular expressions to match known, safe domains and techniques for handling preflight requests and subdomains, alongside other security considerations.
It is important to validate and sanitize the origin header, avoid wildcards for “Access-Control-Allow-Origin” unless data is truly public, and ensure server responses correctly to preflight requests.