CSPViolationReport: effectiveDirective property

Value

A string representing the effective Content-Security-Policy directive that was violated.

Examples

CSP inline script violation

This example triggers a CSP violation using an inline script, and reports the violation using a ReportingObserver. In particular, it logs the effectiveDirective and the originalPolicy, making the difference clear.

HTML

The HTML file below uses the <meta> element to set the Content-Security-Policy default-src to self, which allows scripts and other resources to be loaded from the same domain, but does not allow inline scripts to be executed. The document also includes an inline script, which should trigger a CSP violation.

<!doctype html>
<html lang="en">
  <head>
    <meta
      http-equiv="Content-Security-Policy"
      content="default-src 'self'; report-to csp-endpoint" />
    <meta
      http-equiv="Reporting-Endpoints"
      content="csp-endpoint='https://example.com/csp-reports'" />
    <script src="main.js"></script>
    <title>CSP: Violation due to inline script</title>
  </head>
  <body>
    <h1>CSP: Violation due to inline script</h1>
    <script>
      const int = 4;
    </script>
  </body>
</html>

JavaScript (main.js)

The document above also loads the external script main.js, which is shown below. Because this is loaded from the same domain as the HTML, it is not blocked by the CSP.

The script creates a new ReportingObserver to observe content violation reports of type "csp-violation". Each time the callback function is invoked, we get the body of the first entry of the reports array, and use it to log the effectiveDirective and originalPolicy of the violation to the console.

// main.js
const observer = new ReportingObserver(
  (reports, observer) => {
    console.log(`effectiveDirective: ${reports[0].body.effectiveDirective}`);
    // effectiveDirective: script-src-elem
    console.log(`originalPolicy: ${reports[0].body.originalPolicy}`);
    // originalPolicy: default-src 'self'; report-to csp-endpoint
  },
  {
    types: ["csp-violation"],
    buffered: true,
  },
);

observer.observe();

Note that while there might be multiple reports in the returned array, for brevity we only log the values of the first element.

Results

The console output for the above code is:

effectiveDirective: script-src-elem
originalPolicy: default-src 'self'; report-to csp-endpoint

Note that the originalPolicy matches the <meta> content of the Content-Security-Policy directive in the HTML, and specifies that the policy is self by default (default-src 'self').

The effectiveDirective is script-src-elem, which specifies valid sources for JavaScript <script> elements. This is the specific directive that has effectively been violated, even though default-src was set in the policy.

Specifications

Browser compatibility

See also

• SecurityPolicyViolationEvent.effectiveDirective