.tip

May 21, 2026 · one of the small things

X-Content-Type-Options and Content-Disposition on user uploads

A user uploads an HTML file named photo.png. A browser that sniffs content types renders it, with your origin's cookies.

X-Content-Type-Options: nosniff
Content-Disposition: attachment; filename="photo.png"

Better still, serve uploads from a separate domain. The two headers are the minimum on the same one.

securityhttp

~/tips/today — 2026-09-04

~cat tips/today

Session cookies: HttpOnly, Secure, SameSite=Lax

securityhttp

Three attributes, each closing a class of attack. HttpOnly keeps scripts from reading it. Secure keeps it off plain HTTP. SameSite=Lax stops it being sent on cross-site POSTs, which is most CSRF.

Set-Cookie: session=...; HttpOnly; Secure; SameSite=Lax; Path=/; Max-Age=1209600

Strict breaks arriving from an external link while logged in. Lax is the default worth keeping.

↵ open y yesterday l ls /tips

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