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InfoQ Homepage News Mozilla's Observatory Website Security Analysis Tool Available

Mozilla's Observatory Website Security Analysis Tool Available

Mozilla has launched a new website security analysis tool, Observatory, in the hopes of encouraging developers and sys admins to boost their website security configurations.

The premise is simple: enter the URL of a website and the tool will connect and analyze the HTTP headers, providing a numerical score and letter grade. There are a number of properties that the site looks at and for each one a negative score modifier is imposed depending on the severity of the problem. The top level checks are:

  • Cookies
  • Cross-origin Resource Sharing (CORS)
  • Content Security Policy
  • HTTP Public Key Pinning
  • HTTP Strict Transport Security
  • Redirections
  • Subresource Integrity
  • X-Content-Type-Options
  • X-Frame-Options
  • X-XSS-Protection

According to scoring details from Mozilla, each site starts with a score of 100 and loses or gains points depending on its configuration:

All websites start with a baseline score of 100, and then receive penalties or bonuses from there. Although the minimum score is 0, there is no maximum score. Currently, the highest possible score in the HTTP Observatory is 130. Note that although both the letter grade ranges and modifiers are essentially arbitrary, they are based on feedback from industry professionals on how important passing or failing a given test is likely to be.

For example, in the CORS test, a site with CORS headers but restricted to specific domains receives no negative points for that criteria. However, if the same site allows all domains while using a CORS XML file, a negative 50 points are applied; the largest such negative modifier.

Observatory is broken down into a core library, a CLI, and a web interface. The CLI lets developers script the scoring of their website into a test suite or deployment logic. For more casual observers, the web interface has an input box for the website address as well as some options. The tool can also reach out to other security analyzers such as and to provide more in depth coverage.

On the website, each category has a link to Mozilla's documentation on the topic where developers can find solid guidance on how to best implement the security practices. Mozilla's guidance on CORS says:

[CORS information] should not be present unless specifically needed. Use cases include content delivery networks (CDNs) that provide hosting for JavaScript/CSS libraries and public API endpoints. If present, they should be locked down to as few origins and resources as is needed for proper function.

The Observatory site itself receives an A+ with a score of 120 while receives a D+ with a score of 40. The project is open source and available on GitHub.

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