Apollo Embedded Sandbox and Explorer vulnerable to CSRF via window.postMessage origin-validation bypass

QFinch assessment

A **Cross-Site Request Forgery (CSRF)** vulnerability was identified in Apollo’s **Embedded Sandbox** and **Embedded Explorer**.

Potential impact

A Cross-Site Request Forgery (CSRF) vulnerability was identified in Apollo’s Embedded Sandbox and Embedded Explorer. The vulnerability arises from missing origin validation in the client-side code that handles window.postMessage events. A malicious website can send forged messages to the embedding page, causing the victim’s browser to execute arbitrary GraphQL queries or mutations against their GraphQL server while authenticated with the victim’s cookies. Who is impacted Anyone embedding Apollo Sandbox or Apollo Explorer in their website may have been affected by this vulnerability. - Users who embed Apollo Sandbox or Apollo Explorer in their websites via npm packages (@apollo/sandbox and @apollo/explorer) or direct links to Apollo’s CDN. - Users running Apollo Router with embedded Sandbox enabled. This served the vulnerable code from Apollo’s CDN. - Users running Apollo Server with embedded Sandbox or Explorer enabled. Embedded Sandbox is enabled by default when NODEENV is not set to production, and embedded Sandbox and Explorer can also be enabled in production mode via landing page plugins. This served the vulnerable code from Apollo’s CDN. While all of the above methods of serving Embedded Sandbox and Explorer were vulnerable, Apollo has already updated its CDN to remove all vulnerable versions. Unless you install the npm package @apollo/sandbox or @apollo/explorer directly into your website’s front end code, no action is necessary: the vulnerability has already been mitigated. Users who do not embed Sandbox/Explorer on their websites, or who only run Apollo Router/Server with production defaults were never impacted. The use of non-embedded Sandbox and Explorer hosted on studio.apollographql.com is not vulnerable. Scope of impact The vulnerability allows a malicious website to open the vulnerable website in a new window and force it to send GraphQL requests to its origin. The requests themselves are not "cross-origin" as they are directly issued from the vulnerable website, but their contents are dictated by the malicious website. The malicious website cannot read the responses to the GraphQL operations, but the operations may be mutations with side effects (such as using credentials to update app-specific data access controls). These operations can contain the browser user's cookies, and the vulnerable website may be on a private network otherwise inaccessible to the attacker. Operations sent this way look and exactly like legitimate operations sent by a human interacting with the embedded Sandbox or Explorer.