The item said SameSite=Lax was "enough for modern browsers" but wrong "on a
downgrade to an old browser or unusual proxies", which named the least likely
scenario and missed the most likely one: SameSite is scoped to the registrable
domain, not the origin. The panel runs on a subdomain, so any page anywhere
under the operator's domain — the CMS on www, a stale CNAME, a neighbouring
service — is same-site and its POST carries the session cookie.
It also said nothing about what a successful CSRF would actually buy. Almost
everything is a blind write the attacker cannot read, except POST
/domains/import: multipart is a CORS-simple content type, and a domain export
carries a DKIM key and working SASL passwords, so an attacker uploads
credentials they already know and gains a sending identity on someone else's
relay. That single endpoint, not the destructive ones, is what sets the bar.
The options now carry their cost and their limits: an Origin/Sec-Fetch-Site
check in the phase 14.A middleware closes the subdomain case for ~15 lines,
while a naive double-submit token does not close it at all, since a same-site
neighbour can write the parent domain's cookie. Route facts, cookie
attributes, the export struct and the absence of any hx-post were checked
against the code rather than assumed.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
mix
3531a6694c