CORS mistakes that break internal dashboards

Internal dashboards are where bad CORS habits go to hide. I’ve seen teams lock down customer-facing APIs pretty well, then turn around and ship an admin panel that talks to five internal services with Access-Control-Allow-Origin: *, cookies flying around, and preflights failing randomly because nobody remembers which proxy strips which header. Internal tooling feels “safe” because it lives behind SSO, VPN, or a corporate network. That mindset causes sloppy CORS configs. Browsers don’t care that your app is “internal.” They still enforce the same rules, and attackers love soft targets with elevated access. ...

May 21, 2026 · 7 min · headertest.com