Impact

What kind of vulnerability is it? Who is impacted?

This is an XSS vulnerability that has the potential to impact anyone rendering a component directly from a controller with the view_component gem. Note that only components that define a #call method (i.e. instead of using a sidecar template) are affected. The return value of the #call method is not sanitized and can include user-defined content.

In addition, the return value of the #output_postamble method is not sanitized, which can also lead to XSS issues.

Patches

Has the problem been patched? What versions should users upgrade to?

Versions 3.9.0 has been released and fully mitigates both the #call and the #output_postamble vulnerabilities.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

Sanitize the return value of #call, eg:

class MyComponent < ApplicationComponent
  def call
    html_escape("<div>#{user_input}</div>")
  end
end

References

Are there any links users can visit to find out more?

#1950

For more information

If you have any questions or comments about this advisory:

Open an issue in the github/view_component project.