# Security considerations ## Stable social account identifiers Social authentication associations are authorization bindings. Their `uid` must therefore come from a provider identifier that is immutable and cannot be reassigned, rather than a display name, email address, UPN, or other human-readable login name. Bundled backends use stable provider identifiers where available, including OIDC `sub` claims, provider account IDs, UUIDs, and verified OpenID identity URLs. Applications overriding a backend’s `ID_KEY` are responsible for ensuring the selected claim has the same stability properties. Backends whose provider responses expose no stable identifier, including Drip, Last.fm, and Mixcloud, are association-only and require an authenticated local user. When upgrading an existing deployment, read [the configurable user ID key documentation](configuration/settings.html.md#configurable-user-id-key) before authenticating users. The default compatibility migration preserves existing logins but accepts a one-time first-login race for associations that lack stored stable identity data. Security-sensitive deployments should disable that fallback and migrate the affected records administratively. ## Host header validation The library may use the incoming HTTP `Host` header when generating absolute URLs or redirects during the authentication and authorization flow. If the `Host` header is not validated by the deployment stack, it may allow host header injection attacks. This is a deployment and configuration concern rather than a defect in the library itself. The behavior is intentional, as the library needs to construct absolute URLs for OAuth callbacks and redirects. Proper upstream validation is required to ensure that only legitimate `Host` header values are accepted by your application. ## Reverse proxy configuration When deploying behind a reverse proxy (such as nginx, Apache, HAProxy, or a cloud load balancer), the proxy must validate the Host header before forwarding requests to the application. Key requirements: * **Validate the Host header**: Only expected hostnames should be forwarded upstream to the application. Requests with unexpected or malicious Host values should be rejected by the proxy. * **Forwarded headers**: If your deployment uses forwarded headers such as `X-Forwarded-Host` or the standard `Forwarded` header: * These headers must be accepted **only from trusted proxies**. * They must **not** be blindly trusted from direct client requests. * They must be configured explicitly in the proxy configuration. #### NOTE Configuration syntax varies across reverse proxy implementations. Consult your proxy’s documentation for Host header validation and forwarded header handling. ## Django configuration When using Python Social Auth with Django, proper Host header validation must be configured at the application level using Django’s built-in security features. Key requirements: * **Configure ALLOWED_HOSTS**: The `ALLOWED_HOSTS` setting must be explicitly configured with the canonical hostname(s) for your application. For example: ```default ALLOWED_HOSTS = ['example.com', 'www.example.com'] ``` * **Never use wildcard in production**: The wildcard value `"*"` must not be used in production environments, as it disables Host header validation entirely. * **Host validation behind proxies**: Host validation must remain enabled even when the application is deployed behind a reverse proxy. Do not disable `ALLOWED_HOSTS` validation based on the assumption that the proxy will handle it. * **Forwarded header settings**: If your deployment uses forwarded headers, configure Django’s `USE_X_FORWARDED_HOST` setting carefully. This setting should only be enabled when: * The application is behind a trusted reverse proxy. * The proxy is properly configured to set or strip forwarded headers. * The proxy prevents clients from sending malicious forwarded headers directly. For more information on Django security settings, refer to the [Django security documentation](https://docs.djangoproject.com/en/stable/topics/security/).