Bug: the per-browser pie was stored under a single global key
(`cassandra.pie`) with no per-user scope. If User A uploaded a
portfolio and User B then signed in on the same browser, User B saw
User A's holdings — portfolio.js read straight from localStorage on
hydration with no check that the data belonged to the current session.
This was not a server-side leak: the session cookie was correct, no
API returned User A's data to User B. The stale browser state was the
sole vector. Reported by the operator while testing the paid-checkout
flow with a second account on the same browser.
Fix — defense in depth, two layers:
1. base.html now stamps cu.user.id into localStorage as
`cassandra.user_id` on every authenticated page load. If the
previous stamp doesn't match the current user, wipe localStorage
(preserving only `cassandra.theme`, which is cosmetic) and
sessionStorage before any other script runs. This catches:
- the reported scenario (User A logs out, User B logs in)
- any case where logout missed the wipe (JS disabled, browser
killed before the redirect ran)
- cookie-revocation / session-rotation edge cases where the
server-side identity changes without an explicit logout
2. /logout no longer returns a bare 303; it returns a small HTML
page that actively wipes per-user localStorage + sessionStorage
client-side (theme preserved), then redirects to /login. A
meta-refresh covers the no-JS case (the cookie deletion is
still server-side, so security is preserved either way).
Behaviour for the legitimate case (same user logs out + back in)
is unchanged: their localStorage data survives because the
mismatch check sees the same user_id and doesn't fire — the
logout wipe runs but they re-stamp + re-upload only the
cassandra.user_id and a fresh pie cycle if they choose to upload.
Suite: 221 passed, 5 skipped, 0 failed.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Giorgio Gilestro
62960d5bea