# XShop – Security

## 1. Principles

- Sanitize in, validate, escape out.
- Nonce + capability for every state-changing request.
- Use WP/WC APIs; no hand-rolled auth/crypto.

## 2. Input

- `sanitize_text_field`, `sanitize_textarea_field`, `sanitize_email`, `wc_clean`, `absint`, `esc_url_raw` per type.
- Validate: enums via allow-list, URLs via `wp_http_validate_url` where remote, dates via `DateTimeImmutable`.
- No `$_GET`/`$_POST` without sanitization. No `extract()`.

## 3. Output

- `esc_html`, `esc_attr`, `esc_url`, `esc_html__`, `wp_kses_post` (only for intentionally HTML fields with allow-list), `wp_kses` for narrow HTML.
- No `echo $raw`.

## 4. CSRF

- Every POST/AJAX/REST mutation: `check_ajax_referer` / `wp_verify_nonce` / `X-WP-Nonce` header for REST.
- REST: `permission_callback` checks nonce and capability.

## 5. AuthZ

- Admin screens: `current_user_can('manage_options')` or `manage_woocommerce` where appropriate (documented per screen).
- Q&A: `edit_posts` for moderation; user can delete own question via `delete_post` cap check.
- Banners: `manage_options`.

## 6. XSS

- No inline `onclick` with untrusted data. No `innerHTML` with unsanitized server data – DOM via `textContent` or sanitized fragment.
- Stored XSS: banner CTA/link, Q&A body – sanitized on save, escaped on render.

## 7. SQLi

- No raw SQL unless via `$wpdb->prepare`. Prefer `WP_Query`/`WC` CRUD. No string-concatenated queries.

## 8. Special Cases

- **File uploads**: use `wp_handle_upload` + `wp_check_filetype`, no arbitrary file execution, no path traversal (`sanitize_file_name`, `realpath` check).
- **Redirects**: `wp_safe_redirect` + `wp_validate_redirect` allow-list.
- **Unserialize**: never `unserialize` user data; use JSON.
- **Secrets**: no inline secrets; no committed `.env`.
- **Remote import**: validate MIME, size cap, timeout, no SSRF (allow-list demo asset host if any).

## 9. Headers (theme-level)

- Theme does not override server headers; document recommended headers for host (CSP, etc.) in `docs/security.md`.

## 10. Checklist per Feature

- [ ] Inputs sanitized + validated
- [ ] Nonce verified
- [ ] Capability checked
- [ ] Outputs escaped
- [ ] No raw SQL
- [ ] No unsafe redirect/unserialize/upload

## 11. Search Security Review (M3 — 2026-09-13)

- **Endpoint**: `GET /wp-json/xshop/v1/search` `permission_callback __return_true` — public read-only, no auth needed (visitors must search). No private data: only `id/title/url/image/price_html/type/in_stock` from published products; no `post_password`, no customer/order/user, no draft/private (`post_status=publish` enforced), no internal meta beyond `_sku` LIKE. Verified via direct REST: draft products never returned.
- **Sanitization**: `search` via `sanitize_text_field` + `wp_strip_all_tags` + `mb_substr 100` + `trim`; `limit` via `absint` 1..20; bounded length prevents DOS via huge query.
- **Validation**: `search` max 100 chars, `limit` validate 1..20 else 400 (WP REST validation). Minimum length 2 enforced in handler returns empty 200 without DB query.
- **Escaping**: `title` via `html_entity_decode` + JS `textContent`, `url` via `get_permalink` + `esc_url` in handler `price_html` from Woo (trusted but passed as HTML; frontend injects via `innerHTML` after ensuring no script — price_html contains only Woo spans, no user input).
- **Abuse**: public endpoint can be crawled; mitigated via `Cache-Control: public, max-age=60`, limited `posts_per_page` (`limit*2` max 40), `no_found_rows:true`, no full table scan (indexed `s` + `meta_query` on `_sku` with LIKE). No N+1 (IDs then single `wc_get_product` per result, max 6). Recommend rate limiting at reverse proxy for high traffic.
- **XSS**: `search` never reflected unescaped; response JSON; frontend uses `textContent` for title.

## 12. Review Process

- PHPCS `WordPress.Security` + manual review before each release.
- Security note in CHANGELOG.md.