view_component is a framework for building reusable, testable, and encapsulated view components in Ruby on Rails. Versions prior to 3.9.0 and 2.83.0 have a cross-site scripting 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` methodis not sanitized, which can also lead to cross-site scripting issues. Versions 3.9.0 and 2.83.0 have been released and fully mitigate both the `#call` and the `#output_postamble` vulnerabilities. As a workaround, sanitize the return value of `#call`.

Affected: RubyGems: view_component

### 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](https://viewcomponent.org/guide/templates.html#call) (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](https://viewcomponent.org/api.html#output_postamble--string) 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:

```ruby 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?_

https://github.com/ViewComponent/view_component/pull/1950

### For more information

If you have any questions or comments about this advisory:

Open an issue in the [github/view_component](https://github.com/github/view_component) project.