Insufficient Verification of Data Authenticity

Summary

The `fetch()` API and navigation incorrectly shared the same cache, as the cache key did not include the optional headers `fetch()` may contain. Under the correct circumstances, an attacker may have been able to poison the local browser cache by priming it with a `fetch()` response controlled by the additional headers. Upon navigation to the same URL, the user would see the cached response instead of the expected response. This vulnerability affects Firefox < 123.