Mesh Connect JS SDK Vulnerable to Cross Site Scripting via createLink.openLink

Summary

The lack of sanitization of URLs protocols in the createLink.openLink function enables the execution of arbitrary JavaScript code within the context of the parent page.

Details

https://github.com/FrontFin/mesh-web-sdk/blob/cf013b85ab95d64c63cbe46d6cb14695474924e7/packages/link/src/Link.ts#L441 The createLink.openLink function takes base64 encoded links, decodes them, and then sets the resulting string as the src attribute of an iframe. It’s important to note that the protocol part is not validated, so a payload, which is a valid URL, such as javascript:alert(document.domain)//, can be provided to the function.

PoC

1. Extract poc-mesh-web-sdk.zip
2. Run yarn install and then yarn start
3. Paste this payload inside the input box: amF2YXNjcmlwdDphbGVydCh3aW5kb3cucGFyZW50LmRvY3VtZW50LmJvZHkuZ2V0RWxlbWVudHNCeVRhZ05hbWUoImgyIikuaXRlbSgwKVsiaW5uZXJIVE1MIl0pLy8=
4. Click on the OpenLink button
5. Notice the alert box and ability to access the h2 title from the parent page

It can also be verified via https://paylink.meshconnect.com/?linkToken=amF2YXNjcmlwdDphbGVydCgpLy8=.

Impact

This is technically indistinguishable from a real page at the rendering level and allows access to the parent page DOM, storage, session, and cookies. If the attacker can specify customIframeId, they can hijack the source of existing iframes.

If access to the private key is possible or if transactions are tampered with or initialized, in a wallet context, it can result in a critical impact due to loss of funds scenarios.

Reporters

• Amine zwxxb Elsassi of Aptos Labs