# Security

Scrapy defaults are optimized for web scraping, not for the security posture that you might expect from software that handles untrusted input or runs in a shared or exposed environment. Some common security practices are unnecessary for many scraping use cases, and a few can even prevent valid ones (for example, sites that you must scrape may use misconfigured TLS certificates or serve content over unencrypted protocols).

This page highlights the Scrapy defaults that have security implications, so that you can make an informed decision about whether to keep them, and explains how to harden them along with the trade-offs involved.

Note

None of the options below are silver bullets. Which of them make sense depends on your threat model: whether the URLs you crawl come from trusted sources, whether the machine running Scrapy is exposed to a network you do not control, whether the data you handle is sensitive, and so on.

## Treat responses as untrusted input

Regardless of any setting, remember that response data comes from servers you do not control, even when you trust the site you are crawling, as responses may be tampered with in transit or the server itself may be compromised.

Never pass response data to functions that can execute code or otherwise act on their input in an unsafe way, such as `eval()`, `exec()`, or `pickle.loads()`, and be careful when writing response data to paths derived from the response itself.

## TLS connections

### Certificate verification

By default Scrapy does not verify the TLS certificate of HTTPS servers, as controlled by the `DOWNLOAD_VERIFY_CERTIFICATES` setting (default: `False`).

This default favors reach over security: many sites that are otherwise fine to scrape have expired, self-signed, or otherwise invalid certificates, and verifying certificates would make requests to them fail.

If the integrity of the connection matters to you (for example, to detect man-in-the-middle attacks), set:

    DOWNLOAD_VERIFY_CERTIFICATES = True

- Pro: requests to servers with invalid or untrusted certificates fail instead of silently succeeding, protecting you from some man-in-the-middle attacks.

- Con: you can no longer scrape sites with misconfigured certificates without re-disabling verification for them.

### Protocol versions and ciphers

You can restrict the TLS protocol versions that Scrapy accepts through the `DOWNLOAD_TLS_MIN_VERSION` and `DOWNLOAD_TLS_MAX_VERSION` settings, e.g. to reject obsolete protocol versions.

By default Scrapy uses the OpenSSL `DEFAULT` cipher list (`DOWNLOADER_CLIENT_TLS_CIPHERS`), which favors compatibility and still allows some older, weaker ciphers. Set it to `None` to instead use the curated cipher list of the underlying TLS implementation (Twisted), which excludes weak ciphers:

    DOWNLOADER_CLIENT_TLS_CIPHERS = None

- Pro: connections that would negotiate a weak cipher fail instead of succeeding.

- Con: you can no longer connect to servers that only support the excluded ciphers.

## Unencrypted protocols

By default Scrapy enables download handlers for unencrypted protocols, namely `http://` and `ftp://` (see `DOWNLOAD_HANDLERS_BASE`). Data sent and received over these protocols, including any credentials, travels in plain text and can be read or modified by anyone on the network path.

If you only crawl over encrypted protocols, you can disable the unencrypted ones so that no request can accidentally be sent unencrypted:

    DOWNLOAD_HANDLERS = {
        "http": None,
        "ftp": None,
    }

- Pro: a misconfigured or maliciously-redirected request cannot leak data over an unencrypted connection, as such requests fail instead.

- Con: you can no longer crawl resources that are only available over those protocols.

Note that disabling the `http` handler also prevents plain-HTTP requests that result from following an `http://` redirect or link, which is often the point of disabling it.

## Local and non-network resources

By default Scrapy enables download handlers for the `file://` and `data:` schemes (see `DOWNLOAD_HANDLERS_BASE`). The `file://` handler reads arbitrary files from the local filesystem, limited only by the permissions of the process running Scrapy.

This is convenient (for example, to parse a local HTML file), but it is a risk if any of the URLs you schedule come from an untrusted source: a crafted `file:///etc/passwd` URL could read local files.

If you do not need them, disable these handlers:

    DOWNLOAD_HANDLERS = {
        "file": None,
        "data": None,
    }

- Pro: crawled URLs cannot be used to read local files or inline data.

- Con: you can no longer fetch `file://` or `data:` URLs.

More generally, if you crawl URLs from untrusted sources, consider validating their schemes (and, where applicable, their hosts) before scheduling requests, to avoid server-side request forgery (SSRF) and similar issues.

## Telnet console

Scrapy enables the telnet console by default (`TELNETCONSOLE_ENABLED`). The telnet console is a Python shell running inside the Scrapy process, so anyone who can connect to it can run arbitrary code in that process.

By default the console binds to `127.0.0.1` (`TELNETCONSOLE_HOST`) and is protected by a username (`TELNETCONSOLE_USERNAME`, default `scrapy`) and an automatically generated password (`TELNETCONSOLE_PASSWORD`), so it is only reachable from the local machine.

Warning

Telnet does not provide any transport-layer security, so the username/password authentication does not protect the credentials or the session from anyone able to observe the traffic. Never expose the telnet console over an untrusted network by changing `TELNETCONSOLE_HOST` to a non-local address.

If you do not use the telnet console, disable it entirely:

    TELNETCONSOLE_ENABLED = False

- Pro: removes a local code-execution surface and one less listening port.

- Con: you can no longer inspect and control a running crawler through it.

## Credential leakage across domains

Some Scrapy features attach credentials or other sensitive headers to requests, and a crawl that spans multiple domains can leak them to unintended hosts:

- HTTP authentication credentials set through `HttpAuthMiddleware` are only sent to the domain set in `HTTPAUTH_DOMAIN`. Leave this set to the intended domain rather than `None` so that credentials are not sent to every domain you crawl.

- The `Referer` header may disclose the URLs you crawl to other sites. The default `REFERRER_POLICY` already avoids sending the referrer from HTTPS to HTTP, but you can tighten it further (for example, to `same-origin` or `no-referrer`) if needed.