Content Security Policy (CSP) Explained

Content Security Policy is a standard of computer security that came into existence for preventing the cross-site scripting or XSS, code injection attacks and click-jacking. It is an added security layer that assists in detecting and mitigating the several attacks types. The use of attacks is for everything that is from the theft of data to the defacement of the site to the malware distribution.

Content Security Policy

Content security policy is the candidate recommendation of W3C which is a group working on the security of web application. CSP offers the standard method for the owners of the website for declaring the content origins that are approved.

Another aspect of CSP is a way for selectively specifying that which content needs to be loaded in the applications of a web. One can do this with the use of hashes, nonces and whitelisting.

How does Content Security Policy work?

The specifying of a Content Security Policy is workable through the website of the HTTP response header by the developer. A browser of a web that supports the content security policy like Firefox, Chrome is something that leads to parsing the information.

The noteworthy element is an approach that is whitelist that includes the instructions such as particular domains, hashes, nonces, and inline scripts that needs to be present and valid for the loading of content.

What kinds of Web Application Vulnerabilities can Customer Security Policy Prevent?

Content Security Policy can efficiently prevent the vulnerabilities like cross-site, issues of mixed content security, click-jacking, the downgrading of protocol and any other form of injection of code. Thus, it is the result of content injection that is not trustworthy into the resource that is trustworthy.

Here are the examples of methods that are different for implementing the Content Security Policy in the web applications:

Domains whitelisting

It is an instance of whitelisting that allow inline scripts and loading of the scripts from Content-Security-Policy: script-src ‘self’

Use of hashes

The activation is through the use of nonce-$random_value in the header response of HTTP. See below:

Content-Security-Policy: script-src ‘self’ ‘nonce-bmV0c3BhcmtlciBydWxlcyA7KQ==’

Certainly, it is vital that the nonce is strong with the cryptographically secure functionality for ensuring as it is not predictable.


Furthermore, CSP is configurable for loading resources if they match the defining hashes. It is maybe not probable for executing the resources easily and for setting such as the use of the following header of CSP is usable also:

Content-Security-Policy: script-src ‘self’ ‘sha256-78iKLlw3hSqddlf6qm/PGs1MvBzpvIEWioaoNxXIZwk=’

Put it all together

Hence, Content Security Policy is becoming one of the well-known policies that helps in removing the susceptibilities of cross-site. It helps the developers in ensuring that there are no injection attacks for the website. Therefore, if you intend to integrate the policy, then don’t wait.


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