Reflected XSS in GraphQL Playground
Advisory: GHSA-4852-vrh7-28rf (CVE-2020-4038)
Published: 2020-06-09T00:24:57Z

### Impact

**directly impacted:**

- `graphql-playground-html@<1.6.22` - all unsanitized user input for `renderPlaygroundPage()`

**all of our consuming packages** of `graphql-playground-html` are impacted:

- `graphql-playground-middleware-express@<1.7.16` - unsanitized user input to `expressPlayground()`
- `graphql-playground-middleware-koa@<1.6.15` - unsanitized user input to `koaPlayground()`
- `graphql-playground-middleware-lambda@<1.7.17` - unsanitized user input to `lambdaPlayground()`
- `graphql-playground-middleware-hapi@<1.6.13` - unsanitized user input to `hapiPlayground()`

as well as ***any other packages*** that use these methods with unsanitized user input.

**not impacted:**

- `graphql-playground-electron` - uses `renderPlaygroundPage()` statically for a webpack build for electron bundle, no dynamic user input
- `graphql-playground-react` - usage of the component directly in a react application does not expose reflected XSS vulnerabilities. only the demo in `public/` contains the vulnerability, because it uses an old version of the html pacakge.

### Patches

upgrading to the above mentioned versions will solve the issue.

If you're using `graphql-playground-html` directly, then:

```
yarn add graphql-playground-html@^1.6.22
```

or

```
npm install --save graphql-playground-html@^1.6.22
```

Then, similar steps need to be taken for each middleware:

- [Upgrade Express Middleware](https://www.npmjs.com/package/graphql-playground-middleware-express#security-upgrade-steps)
- [Upgrade Koa Middleware](https://www.npmjs.com/package/graphql-playground-middleware-koa#security-upgrade-steps)
- [Upgrade Lambda Middleware](https://www.npmjs.com/package/graphql-playground-middleware-lambda#security-upgrade-steps)
- [Upgrade Hapi Middleware](https://www.npmjs.com/package/graphql-playground-middleware-hapi#security-upgrade-steps)

### Workarounds

Ensure you properly sanitize *all* user input for options you use for whatever function to initialize GraphQLPlayground:

for example, with `graphql-playground-html` and express:

```js
const { sanitizeUrl } = require('@braintree/sanitize-url');

const qs = require('querystringify');

const { renderPlaygroundPage } = require('graphql-playground-html');

module.exports = (req, res, next) => {
	const { endpoint } = qs.parse(req.url)
	res.html(renderPlaygroundPage({endpoint: sanitizeUrl(endpoint) })).status(200)
	next()
}
```

or, with `graphql-playground-express`:

```js
const { expressPlayground } = require('graphql-playground-middleware-express');
const { sanitizeUrl } = require('@braintree/sanitize-url');

const qs = require('querystringify');

const { renderPlaygroundPage } = require('graphql-playground-html');

module.exports = (req, res, next) => {
	const { endpoint } = qs.parse(req.url)
	res.html(expressPlayground({endpoint: sanitizeUrl(endpoint) })).status(200)
	next()
}
```

### References

- [OWASP: How to Test for CSS Reflection Attacks](https://github.com/OWASP/wstg/blob/master/document/4-Web_Application_Security_Testing/07-Input_Validation_Testing/01-Testing_for_Reflected_Cross_Site_Scripting.md)
- [Original Report from Cure53](https://user-images.githubusercontent.com/1368727/84191028-dfb7b980-aa65-11ea-8e18-4b8706f538e2.jpg) (jpg)


### Credits

Masato Kinugawa of Cure53

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [graphql-playground](https://github.com/prisma-labs/graphql-playground/issues/new/choose)
* Email us at [rikki.schulte@gmail.com](mailto:rikki.schulte@gmail.com)


Severity: type: CVSS_V3
score: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N
Affected packages:
package: ecosystem: npm, name: graphql-playground-html, ranges: type: ECOSYSTEM, events: introduced: 0
fixed: 1.6.22