GeckoViewContentChannelParent::Init reconstructs a URI from IPC arguments via ipc::DeserializeURI(aArgs.uri()) and then proceeds to open a channel for it in the privileged parent process, without ever verifying that the URI’s scheme is actually content. The invariant that a content channel actor must only ever operate on content:// URIs was never enforced, so a compromised or malicious child process could hand this parent-only actor a URI of any scheme (for example file://) and have the parent open it on the child’s behalf.

The fix adds an early guard, if (!uri || !uri->SchemeIs("content")), that rejects a null URI or any non-content scheme, sets rv = NS_ERROR_UNKNOWN_PROTOCOL, and returns false to fail actor initialization. This works because the scheme is now validated at the trust boundary — inside the parent process, on data received from the child — before any channel is created or resource is touched. The check closes the gap between what the actor is meant to handle and what an attacker can make it handle.

An attacker who controls a child content process can coax the privileged parent into opening URIs outside the intended content:// scheme and reading their contents, yielding information disclosure of local resources on Firefox for Android and Firefox Focus. The disclosure is realized in the parent process on behalf of the sandboxed child, effectively bypassing the child’s scheme/origin restrictions. The precondition is that the attacker already influences the child-to-parent IPC (a compromised or malicious content process), consistent with the classified LogicError and high impact.