I find this highly concerning since:
1. they are crawling potentially sensitive information granted by links with tokens
2. they are triggering potentially harmful and/or confusing actions in your website by repeating links
3. they are repeating requests in a broken way by not encoding url-parameters correctly, for instance url-encoded %2B ends up just as a "+" thus becoming a whitespace (same goes for slashes etc.)
4. I could not find a warning or note on their tracking-pixel documentation that pages tracked would be crawled later
Don't put Facebook tracking on sensitive pages. Actually as a service to your users don't put it anywhere where it doesn't add value.
> 2. they are triggering potentially harmful and/or confusing actions in your website by repeating links
They only perform idempotent[0]* requests which should not have any negative effect if performed multiple times
0: http://restcookbook.com/HTTP%20Methods/idempotency/
* They probably only actually perform GET in reality
So don't put it anywhere.
I'm not a fan of facebook in the slightest, but they are crawling websites they were essentially invited to.
> Again, this only applies to the result, not the resource itself. This still can be manipulated (like an update-timestamp, provided this information is not shared in the (current) resource representation.
This means that tracking is still could potentially affect some stuff, but honestly not by much.
Don't put tracking on sensitive pages.
Do your users, your broken software and yourself a favor and don't put Facebook tracking crap everywhere.
A friend of mine covers this more extensively in this blog post which I found a very interesting read: https://remusao.github.io/posts/static-comments.html
So I think it's still concerning that once they're in, they start crawling. Although not very surprising I have to say... That's their business after all.
There's a bug report regarding the missing header here: https://developers.facebook.com/bugs/1654459311255613/
Unfortunately it seems impossible to get in touch with Facebook devs directly.
Now, if the crawler doesn't honor robots.txt, then you can complain (loudly).
Not their fault. GET requests should not modify anything.
The summary of what most people are saying including some take aways:
- If you put something on the Internet it is public. Period. It is up to you to keep prying eyes away from that page. You can do that with strong mechanisms (like passwords and firewalls) or weak (like robots.txt) but you need to do something. You can't expect a page on the Internet to be private.
- Requests should never ever have anything sensitive in the query string. The query string is inherently logged. By your browser history, your web server, any tracking pixels like Facebook you put on the page, etc. If you absolutely must include a token in the URL (like with OAuth) make sure it is a temporary token and is immediately replaced with something more durable like a cookie or local storage, no unnecessary HTML is rendered, and the user is redirected to a new page that doesn't have it in the URL.
- GET requests should be idempotent. They should avoid changing any data as much as possible and should not have side effects. This is specified directly in the HTTP spec.
- If your page displayed sensitive data it should send the security tokens in a header field (like cookies or authentication). Users who hit the page without that header field should be responded to with a 404.
- Your point #3 is an add one. It is a bug on the Facebook side, yes, but it doesn't support your primary argument. In fact, if they fixed that bug it would make the perceived issues in your primary argument worse.
- Re #4 they don't need to warn you. See the first bullet. If it is on the internet it is public. Skype, Slack, Twitter, Google, all do the same thing.
Best solution is still to block Facebook's infrastructures, as always.
Abuse of power and shady tracking techniques by Facebook? Unheard of! </rant>
Seriously, this cannot be surprising after learning that the Messenger app listens to everything you do, all the time. That's just off the top of my head. They are doing this and much more.
Can you provide some evidence of this happening on Android ?
Also Facebook categorically denies this: http://www.bbc.com/news/technology-41776215
However, I've never seen a non-anecdotal source or even a source that gathers all anecdotes and gives a decent meta-analysis. Would you happen to have one?
The messenger app probably doesn’t listen to you, but it’s abusive in other ways and shouldn’t be uninstalled. The main creepy feature of Facebook apps is that they continuously track your location. That’s a source of much of the creepy targeting that people notice.
Also, Facebook’s weasel-worded response to the issue implies that they do not use pervasive audio targeting, but buy data from people who do. The Wired article that claimed that using audio was impractical is nonsense.
https://www.wired.com/story/facebooks-listening-smartphone-m...
>To make it happen, Facebook would need to record everything your phone hears while it's on.
This assumption treated as an axiom here is false, and it makes the rest of the article inaccurate as well.
I'm not one for conspiracy theories, but the article lists some forms of how it might work and reasons how it would be unfeasible. There are other ways this could work, IMHO.
I would be surprised if service wouldn't index my site after I put one of their pixels on my site.
Also, the same crawler ignores the "User-agent: *" directive in the robots.txt file and you have to add specific rules for it: "User-agent: Adsbot-Google"
Not surprising at all. Would be interesting to see a write up on this.
I would be more surprised to find out that they didn't crawl everything they can, specifically pages that invite them in.
> 1. they are crawling potentially sensitive information granted by links with tokens
If the page contains sensitive information you absolutely should not have code that you do not control (any code loaded from third party hosts, not just facebook's bits).
As a matter of security due diligence if you have third party hosted code linked into any such pages you should remove it with some urgency and carefully review the design decisions that lead to the situation. If you really must have the third party code in that area then you'll need to find a way of removing the need for the tokens being present.
Furthermore, if the information is sensitive to a particular user then your session management should not permit a request from facebook (or any other entity that has not correctly followed your authentication procedure) to see the content anyway.
> 2. they are triggering potentially harmful and/or confusing actions in your website by repeating links
Possibly true, but again that suggests a design flaw in the page in question. I assume that they are not sending POST or PUT requests? GET and HEAD requests should at very least be idempotent (so repeated calls are not a problem) and ideally lack any lasting side effect (with the exception of logging).
> 3. they are repeating requests in a broken way by not encoding url-parameters correctly
That does sound like a flaw, but one that your code should be immune to being broken by. Inputs should always be verified and action not taken unless they are valid. This is standard practise for good security and stability. The Internet is a public place, the public includes both deliberately nasty people and damagingly stupid ones so your code needs to take proper measures to not allow malformed inputs to cause problems.
You can't use "the page isn't normally linked from other sources so won't normally be found by a crawler" as a valid mitigation because the page could potentially be found by a malicious entity via URL fuzzing.
> 4. I could not find a warning or note on their tracking-pixel documentation that pages tracked would be crawled later
A warning would be nice, but again unless they explicitly say they won't do such things I would be surprised to find that they didn't not that they do.
> 1. they are crawling potentially sensitive information granted by links with tokens
If tokens in GET params are your security concept: please leave the entire field.
2. they are triggering potentially harmful and/or confusing actions in your website by repeating links
So you built something that can be triggered by a simple HTTP request and may have a harmful potential? Wow.
3. they are repeating requests in a broken way by not encoding url-parameters correctly
You are kidding right? That's a problem to you? Either your Webserver drops these or your routes don't match, end of story.
4. I could not find a warning or note on their tracking-pixel documentation that pages tracked would be crawled later
Not a problem, you put it on the web and it will be crawled. Did you ever use Chrome? They report every URL you type to the Google Crawler. Read that anywhere lately?
Do you have a source for this? I Googled (!) and found this: https://www.stonetemple.com/google-chrome-discover-pages , which implies the opposite.
I don't use Chrome personally, but I do occasionally dump [none-too critical] preview files on open but otherwise 'hidden' urls on a domain for clients to view. I just find it easier for clients to deal with than inevitably lost passwords, etc, and tend to ask them to let me know when they're done so I can delete the folder.
I'd be interested to know whether their likely use of Chrome means that Google has a pattern of understanding of my domain space!
- marketing wants some tracking, some developers adds it
- ecommerce websites in the real world tend to "need" these tracking/conversion codes
- you do have legitimate get-requests like password-reset links with tokens, also we do use payment providers who send the customers back to us with get links which include payment tokens, newsletter-unsubscribe links are also often simple token links
- and yes normally a get-request should not change anything (at least not when its just repeated) but the sheer fact that they have access to it _and_ are crawling it is bad
my point being that I find it that they would just crawl everything they recorded instead of just crawling pages which are linked publicly or which are targeted in ad-campaigns combined with the fact that they don't warn you about it
There's no way to know which pages are linked publicly without crawling every page for links. So you're right back at square one.
Ultimately if it's on a Internet-facing web server and not hidden behind an IP whitelist or secure login function then you have to assume it is public. All you are arguing is about different degrees of "public" which somewhat misses the real issue of website security.
Some crawlers do deliberately hit random URLs to check how you're handling 404s. Over crawlers are entirely dishonest and will try to find content that wasn't intended to be made public. How are you going to handle them if you're stumped with the Facebook crawlers that you invited onto your site?
> ...combined with the fact that they don't warn you about it
It's pretty obvious behavior in my opinion but maybe they could have been more explicit. However going back to my previous point, no other crawler advertises what it's going to crawl beforehand. So where do you draw the line? Ranting that Google indexed your site? What about visitors buying stuff on your ecommerce package without prior communication requesting access to the site?
You wouldn't ask customers in a bricks-and-mortar store to state their intentions the moment they walked through the shop door so why should every HTTP user agent have to do the same? While web security can be both complex and maddening, responsibility of hardening the site is still yours; not Facebook's.
While two wrongs don't make a right, assuming we accept that facebook is wrong in this instance which I don;t think I do, the code for the page handing out sensitive information to an unauthenticated request or taking action based on malformed inputs is negligent.
"Information wants to be free" is not just a hippie ideal it is a technical warning. Unless you take proper measures to control and protect sensitive data it will find a way out.
Just add a robots file or block the user agent with your firewall.
Where do they draw the line? Why not run a keylogger through embedded like buttons and widgets? That sounds worse, but isn't all that much worse.
I'm not sure about from facebook's side, but from the point of view of how GDPR applies to the side being crawled if they, as custodians of PII and other sensitive data, are handing it out to unauthenticated requests, they might be liable for punishment for lack of due diligence.
