Impact

In certain configurations, Apollo Server serves the client-side web app "GraphQL Playground" from the same web server that executes GraphQL operations. This web app has access to cookies and other credentials associated with the web server's operations. There is a cross-site scripting vulnerability in GraphQL Playground that allows for arbitrary JavaScript code execution in your web server's origin. If a user clicks a specially crafted link to your GraphQL Playground page served by Apollo Server, an attacker can steal cookies and other private browser data.

Details of the underlying GraphQL Playground vulnerability are available in this graphql-playground advisory. (A similar vulnerability exists in the related graphiql project.) This advisory focuses on identifying whether Apollo Server installations are vulnerable and mitigating the vulnerability in Apollo Server; see the other advisories for details on the XSS vulnerability itself.

The impact of this vulnerability is more severe if (as is common) your GraphQL server's origin URL is an origin that is used to store sensitive data such as cookies.

In order for this vulnerability to affect your Apollo Server installation, it must actually serve GraphQL Playground. The integration between Apollo Server and GraphQL Playground is different in Apollo Server 2 and Apollo Server 3. You can tell which version of Apollo Server you are running by looking at the version of the package from which you import the ApolloServer class: this may be apollo-server, apollo-server-express, apollo-server-lambda, etc.

Apollo Server 3

Apollo Server 3 does not serve GraphQL Playground by default. It has a landing page plugin system and the default plugin is a simple splash page that is not vulnerable to this exploit, linking to Apollo Sandbox Explorer. (We chose to change the default because GraphQL Playground is not actively maintained.)

If you are running Apollo Server 3, then you are only vulnerable if you explicitly import the ApolloServerPluginLandingPageGraphQLPlayground plugin and pass it to your ApolloServer's constructor in the plugins array. Otherwise, this advisory does not apply to your server.

Apollo Server 2

Apollo Server 2 serves GraphQL Playground by default, unless the NODE_ENV environment variable is set to production, or if you explicitly configure it via the playground option to the ApolloServer constructor.

Your Apollo Server 2 installation is vulnerable if any of the following is true:

• You pass playground: true to the ApolloServer constructor
• You pass some other object like playground: {title: "Title"} to the ApolloServer constructor
• You do not pass any playground option to the ApolloServer constructor, and the NODE_ENV environment variable is not set to production

Apollo Server 1

Apollo Server 1 included graphiql instead of graphql-playground. graphiql isn't automatically enabled in Apollo Server 1: you have to explicitly call a function such as graphiqlExpress to enable it. Because Apollo Server 1 is not commonly used, we have not done a detailed examination of whether the integration between Apollo Server 1 and graphiql is vulnerable to a similar exploit. If you are still using Apollo Server 1, we recommend you disable graphiql by removing the graphiqlExpress call, and then upgrade to a newer version of Apollo Server.

Patches and workarounds

There are several approaches you can take to ensure that your server is not vulnerable to this issue.

Upgrade Apollo Server

The vulnerability has been patched in Apollo Server 2.25.3 and Apollo Server 3.4.1. To get the patch, upgrade your Apollo Server entry point package to one of the fixed versions; this package may be apollo-server, apollo-server-express, apollo-server-lambda, etc. Additionally, if you depend directly on apollo-server-core in your package.json, make sure that you upgrade it to the same version.

Upgrade Playground version only

If upgrading to the latest version of Apollo Server 2 or 3 quickly will be challenging, you can configure your current version of Apollo Server to serve the latest version of the GraphQL Playground app. This will pin your app to serve a specific version of GraphQL Playground and you will not receive updates to it when you upgrade Apollo Server later, but this may be acceptable because GraphQL Playground is not actively maintained.

The way to do this depends on what version of Apollo Server you're using and if you're already configuring GraphQL Playground.

• Apollo Server 3: If you are using Apollo Server 3, then you are only vulnerable if your serve explicitly calls ApolloServerPluginLandingPageGraphQLPlayground and passes it to the Apollo Server constructor in the plugins array. Add the option version: '1.7.42' to this call, so it looks like:

plugins: [ApolloServerPluginLandingPageGraphQLPlayground({version: '1.7.42'})]

• Apollo Server 2 with no explicit playground option: If you are using Apollo Server 2 and do not currently pass the playground option to new ApolloServer, add a playground option like so:

new ApolloServer({ playground: process.env.NODE_ENV === 'production' ? false : { version: '1.7.42' } })

• Apollo Server 2 with playground: true or playground: {x, y, z}: If you are using Apollo Server 2 and currently pass true or an object to new ApolloServer, pass the version option under the playground option like so:

new ApolloServer({ playground: { version: '1.7.42', x, y, z } })

Disable GraphQL Playground

If upgrading Apollo Server or GraphQL Playground is challenging, you can also disable GraphQL Playground.

In Apollo Server 3, remove the call to ApolloServerPluginLandingPageGraphQLPlayground from your ApolloServer constructor's plugins array. This will replace GraphQL Playground with a simple splash page. See the landing page plugins docs for details.

In Apollo Server 2, add playground: false to your ApolloServer constructor: new ApolloServer({ playground: false }). This will replace GraphQL Playground with an attempt to execute a GraphQL operation, which will likely display an error in the browser.

If you disable GraphQL Playground, any users who rely on it to execute GraphQL operations will need an alternative, such as the Apollo Studio Explorer's account-free Sandbox.

Credit

This vulnerability was discovered by @Ry0taK. Thank you!

The fix to GraphQL Playground was developed by @acao and @glasser with help from @imolorhe, @divyenduz, and @benjie.

For more information

If you have any questions or comments about this advisory:

• Read the graphql-playground advisory
• Open an issue in the apollo-server repo
• If the issue involves confidential information, email us at [email protected]

References

• GHSA-qm7x-rc44-rrqw