Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.33, 21.2.25, and 22.2.1, ServerPlatformLocation in Angular server-side rendering checks for protocol-relative URLs before WHATWG URL normalization. A request path containing a popping dot segment followed by multiple slashes can bypass the raw resolveUrl check and normalize to a pathname beginning with two slashes. When Angular SSR detects a mismatch with the router's final location, it can place that pathname in an HTTP Location header, causing a browser to navigate to an attacker-controlled origin. Affected applications use @angular/platform-server and @angular/ssr and either expose compatible parameter or child route shapes or pass user-controlled navigation targets through infrastructure that preserves the relevant dot segments or semicolons. Pure client-side SPAs are not affected. This issue is fixed in versions 20.3.33, 21.2.25, and 22.2.1.

Affected: npm: @angular/platform-server

An open redirect vulnerability was identified in `@angular/platform-server` when Server-Side Rendering (SSR) is enabled.

When Angular SSR renders an incoming request, URL resolution and platform navigation are managed by `ServerPlatformLocation` using `resolveUrl` (or `parseUrl` in v20). While `resolveUrl` rejected protocol-relative URLs whose raw string directly started with `//`, this check ran *prior* to WHATWG URL normalization.

When a request URL includes a popping dot-segment followed by multiple slashes (such as `/.//evil.test` or serialized from router route shapes like `/.;/(//evil.test)`), the input bypassed the initial `urlStr.startsWith('//')` check. Subsequent WHATWG URL parsing resolved the dot-segments and resulted in a `pathname` starting with `//` (`//evil.test`).

Consequently, `ServerPlatformLocation` stored `pathname = '//evil.test'`. When `@angular/ssr` detected a mismatch between the rendered URL and the router's final location state, it emitted the unnormalized pathname into the HTTP `Location` response header, producing an HTTP 302 redirect with `Location: //evil.test`, which browsers resolve as a protocol-relative navigation off-origin.

### Impact

Successful exploitation allows an unauthenticated remote attacker to craft URLs that trick Angular SSR into redirecting users to an arbitrary external domain.

* **Bypasses Application-Level Guards:** Common application-level validation routines (such as checking `!returnUrl.startsWith('//')` before inv…