The snapshot/vision guards re-check the page URL before returning content,
but browser_console(expression=...) -> _browser_eval returns arbitrary JS
results directly, leaving two same-class bypasses open:
1. Direct fetch: fetch('http://127.0.0.1/secret').then(r=>r.text()) reads
a private endpoint and returns the body — the page URL stays public so
the post-eval recheck never sees it.
2. Navigate-then-read: location.href='http://127.0.0.1/' then a later eval
reads document.body.innerText.
Guard _browser_eval on the same condition as navigate/snapshot/vision
(not local backend, not local sidecar, not allow_private_urls):
- pre-scan the expression for private/always-blocked URL literals
- re-check window.location.href after the eval at both success-return
sites (supervisor fast-path + subprocess fallback)
Probe failures fail-open (matching the snapshot/vision guards).
