CVE-2026-49336

### Summary `@microsoft/kiota-http-fetchlibrary`'s `RedirectHandler` is documented as stripping `Authorization` and `Cookie` from cross-origin redirect targets, but the default `scrubSensitiveHeaders` callback in `RedirectHandlerOptions` uses case-sensitive property deletion (`delete headers.Authorization`, `delete headers.Cookie`) on a headers object that `FetchRequestAdapter.getRequestFromRequestInformation` has already lower-cased. The delete therefore targets keys that do not exist, the scrub is a no-op, and any Bearer token or Cookie attached by a kiota-generated SDK is forwarded to an attacker-controlled host across a 30x redirect. This is reachable in the default middleware chain (`MiddlewareFactory.getDefaultMiddlewares`) with no custom configuration, and applies to every kiota-generated TypeScript SDK that uses `BaseBearerTokenAuthenticationProvider` or any other authentication provider that sets the `Authorization` request header. ### Affected versions `@microsoft/kiota-http-fetchlibrary` `>= 1.0.0-preview.97` (the release that introduced the `defaultScrubSensitiveHeaders` callback, commit `74886cc4`, tagged 2026-02-27) up to and including `1.0.0-preview.101` (latest at filing). The bug was verified end-to-end against the version published on npm: `1.0.0-preview.100`. The case-mismatch primitive (lowercasing in the request adapter) predates the scrub itself — `FetchRequestAdapter.getRequestFromRequestInformation` has lower-cased header keys via `toLocaleLowerCase()` since commit `d612bac2` (2022-12-09). When the scrub was added in 2026-02 it inherited the mismatch. ### Impact - **Bearer token leak across origin.** When a kiota-generated SDK calls a server that the SDK trusts (Microsoft Graph, an internal API, any OAuth2 resource server) and that server returns an HTTP redirect to a different host, the `Authorization: Bearer <token>` header issued by the auth provider is sent in cleartext to the redirect target. The redirect target can be controlled