# Security Headers — nginx/posterg.conf

## Headers in use

| Header | Value | Purpose |
|--------|-------|---------|
| `X-Frame-Options` | `SAMEORIGIN` | Prevent clickjacking |
| `X-Content-Type-Options` | `nosniff` | Prevent MIME-type sniffing |
| `Referrer-Policy` | `strict-origin-when-cross-origin` | Limit referrer leakage |
| `Permissions-Policy` | `geolocation=(), microphone=(), camera=()` | Disable unused browser APIs |

## Intentionally omitted headers

### `X-XSS-Protection`

This header was **removed** (was `"1; mode=block"`).

**Why:** `X-XSS-Protection` is deprecated and removed from all modern browsers
(Chrome 78+, Firefox never implemented it, Edge dropped it). Worse, the
`mode=block` behaviour can be [actively exploited](https://portswigger.net/daily-swig/xss-protection-header-is-no-longer-supported-in-any-major-browser)
to expose response bodies that would otherwise be blocked. Sending it provides
no protection and may introduce risk.

**Correct mitigation:** a proper `Content-Security-Policy` header (todo item #11).

## Pending headers

| Header | Status |
|--------|--------|
| `Content-Security-Policy` | ⏳ todo item #11 |