A page with an opaque origin, such as one its server sandboxes with a Content-Security-Policy, is reported to the background with the origin "null", and Chrome reports a local file as "file://". The background took either as a site, so every such page was one site: a connection remembered for one covered them all, and the phishing check never matched. The background now parses the reported origin and, when it has no host, refuses the request with 4100 like one with no origin, before any method runs. tests/rpcOrigin.test.js sends both, and README's SiteApproval says what is refused. Model: opus-5-5