GHSA-gv2q-mqqv-365m: Angular Service Worker Policy-Bypass & Credential-Stripping Vulnerabilities

An issue in the @angular/service-worker package compromises the integrity of request-policy enforcement during request reconstruction. When the Angular Service Worker intercepts network requests for matched assets, it reconstructs a new Request object using an internal helper function. During this reconstruction process, the helper function strips the strict, client-defined request redirect policy configuration (such as redirect: 'error'), falling back to the browser's default 'follow' strategy. If the target web application makes client-side requests with a strict policy (e.g., expecting a network error instead of automatically following redirects), the service worker will bypass this instruction and automatically follow HTTP 3xx redirects to other destinations. This acts as an unintended proxy/intermediary ("Confused Deputy") and can result in cookie/credential exposure or same-origin session-restricted data leakage if public dynamic routes redirect to sensitive routes. Impact Web applications registering the @angular/service-worker package are vulnerable to this redirect-policy bypass if they make safe client-side fetch calls (such as { redirect: 'error' }) to paths matched by a service worker asset group (such as lazy-loaded JavaScript bundles or dynamic public assets) that can return HTTP redirects to authenticated same-origin secure endpoints. By stripping developer-defined safety boundaries, the service worker allows the browser to transparently query and return data from credentials-guarded resources that should have been blocked at the network barrier. Attack Preconditions To successfully exploit this vulnerability, all of the following application states and parameters must concurrently exist: 1. Active Angular Service Worker: The target application uses @angular/service-worker and has an active registration of ngsw-worker.js inside the client's browser context. 2. Asset Group Matching: An assetGroups pattern in ngsw-config.json encompasses the target