Cross-Site Request Forgery (CSRF) Explained

[@forceboxed]

@4:53 one of the important things to mention here is that the csrf token is good only as long as it is mapped to the user's session ID in the backend. Otherwise, the attacker might simply obtain a valid CSRF token by visiting the main website themself and inject it into the malicious requests. Tying the token to the user's session and validating that on the backend for each request is very important.

[@hydr0nium_]

Seriously cant say it enough. I freaking love your videos

[@kvenk001]

I second that notion

[@justforyoutube1319]

i came from LiveOverflow channel , i so glad to be here ! your channel is interesting , love it . keep up the good work

[@jammincoder]

Man, I tried researching how CSRF attacks worked last year and I never got a solid grasp of it. This video changed that. As a cybersecurity enthusiast and web developer, this is super helpful!

[@yasirhussain1875]

No words to describe how much informational these videos are. Thank you.

[@MaysField]

"Cat-Site Request Forgery"

[@a.yashwanth]

I watched around 15 videos regarding csrf and you are the only one who explained it clearly. Also not everyone stressed on "the browser automatically sends the cookies".

[@shreyanshdesai3152]

truuu

[@kornelijekovac9793]

I still don't understand it. What does it mean? What cookies? All the cookies from all the tabs opened in the browser are sent with all POST requests that are being made on whichever tab?

[@bsmldy8681]

@@kornelijekovac9793 All the cookies from one website will be sent to the server of that website on each request (with website I mean domain, not origin). The most important cookie is the one with the session id (SID), which identifies the user. More about this can be found if you search for "session management".

[@kornelijekovac9793]

@@bsmldy8681 But how can cookies from two different tabs intermingle?

[@bsmldy8681]

not sure what you mean by that

[@dragonballZbigBang]

There's tens of thousands of videos on Csrf but you easily beat all of them. Yet the number of views you got aren't nearly as close as theirs. Niche youtubers like you are ahead of the time. I hope people like you are revered in coming 5 years

[@PwnFunction]

Yeah, late in the game, but it's totally fine, I'm just trying to give somethin back to the community.

[@OviDB]

Look at it now ;)

[@gerolori]

Damn, dude really planted the seed and let it grow

[@sathvikmalgikar2842]

we need more of these. literally a free service to everyone genuinely interested

[@nullpwn]

Wow , I love the graphical explanatory video, really easy to follow and understand in concordance with explication

[@sleepydev4700]

the music and naration in the intro made me feel like I'm discovering a mistery in another new world, lol. great video

[@CYB3Rsynth]

Third video of yours that came up, and perfectly described the concept. Subscribed

[@theawless]

Great content. I can't believe this is free! PS: I love your colour scheme

[@danialabsolute688]

I really enjoyed your theme of explanation and the background music. sounded adventurous

[@rasikagayangunarathna]

I genuinely don't understand why you stop creating videos. Your style is so cool.

[@dogcat6221]

He's back!

[@krantisatyam]

This is one of the best channel I have encountered 😍

[@JoshuaKisb]

was curious if tokens really work since you could just make a GET and read the token then post. glad you answered that question very quickly. awesome video. i will subscribe

[@nivelis91]

You definitely deserve more subs ;)

[@yashdeephinge]

Great Video and your drawing is amazing bro that google logo and the adobe logo was so perfect.

[@miguelnunez1435]

Just came by from watching LiveOverflow's video. I subbed and put on the bell notification on. This channel looks so cool

[@MinusFourmn]

As I understand it, fetch and XHR require `useCredentials` to send the cookies along with the request which needs to be explicitly stated on the CORS header Access-Control-Allow-Credentials. Otherwise cookies are not being sent and the CSRF fails.

[@subhashsarangi]

You are just awesome man. Why doesn't KZbin show such search results at the top. I couldn't find you when I needed but now I am happy. Thanks bro..

[@mitchelline]

Incredibly amazing video as always. Very great explanation, and I love your color choices and how you draw/write everything

[@itsfarseen]

Love the style of explanation!

[@kid_kulafu_1727]

Bruh you need to create more content like this. Also you give example are to fast but over all your the best. 11/10.

[@aminvogue]

Wunderbar...................U r one awsme teacher. Hats off to the effort you put in, for us mere novices.

[@darklord555X]

the best channel, thanks brother for the knowledge

[@ekaterinazakharenkova5826]

Best explanation I've ever heard!

[@casual-corner-k8s]

This is very well explained, appreciated

[@ph0sgene967]

As someone who pioneered csrf in 2007 this is a great video

[@joshuz101]

I often find it hard to focus on educational videos like this, but somehow your videos have all of my attention. Not sure what voodoo you're using but it's working!

[@berakoc8556]

You put lots of effort into your videos. Transitions are amazing. Wonderful production.

[@farzadsole3784]

Amazing content as always, big fan of your videos and tutorials, thank you so much ;D

[@venkaraj]

Crystal clear explanation. Thanks a ton

[@VietnamSteven]

incredibly informative!

[@aayushkubitkar4827]

Came from Stök's channel. Absolutely loving it now! Subscribed and belled👏

[@samuelk3076]

Very nice video, I love the explanation!

[@fairchild9able]

Thanks for making this. Really nice!

[@king998100]

probably the best explanation out there

[@paulcalinovici8808]

Before sending the delete request, isn't the browser sending a preflight OPTIONS request to the server which will return an error and the delete request won't happen anymore ?

[@aakashthakur1415]

I was thinking the same. Ideally CORS would have stopped this.

[@aakash18in]

yes. In case of Ajax request , SOP will stop the request as the preflight will return error

[@ororabrian7106]

yeah. Just as a note, It seems that you can actually send a simple request to the server and the request will go through but you won't be able to read the response due to cors. namely if you don't have any headers on your request but then again that means you won't have any cookies and won't be carrying any state so pretty useless all in all.

[@SunPodder]

As cors is just client sided, for a hacker this isn't difficult to bypass it

[@spicybaguette7706]

@Orora Brian You can still do CSRF for non-authenticated requests, such as an anonymous message on a blog post or something, which is not entirely harmless

[@stanpeng5931]

Such a good video. I love the voice as well: cute and reliable

[@staynjohnson4221]

12:47 I dont understand why the json data + the content type header are first passed through a redirect(?) then to the vulnerable site?

[@peterfarhat5767]

Because simply flash will forward the request as string and then the site will convert it into header and “ key = value “ type so that it would be readable by the API of vuln.com!

[@youarethecssformyhtml]

Because the redirect can send cookies

[@mosesegboh]

you concept and style of teaching is lovely!..keep it up

[@nickdaone]

You need more likes. Your work is needed for every developer.

[@matthewdraevich4214]

Great explained, thanks🔥

[@zb2747]

Great video, to the point and thoroughly explained the main concept.

[@eshaan7_]

Thankyou for your videos. I would very much like to see a video on Insecure CORS and ways to escalate it :)

[@ETbutforreal]

You explained this better than the skillsoft guys, that's for sure

[@playboicartihey]

this is the best. freaking cool

[@dougthefiddler]

Very clear explanation. Thanks!

[@Gigolas88]

wtf you deserve way more likes on this

[@zTech300]

Great explanation bro, Keep up the good work. Wish ya da best.

[@princepatwari365]

Great videos.........Thank you for posting them

[@mahirmolai3834]

Was watching live overflows vid a month ago, and look at me now, watching each video of yours everyday

[@gamingwolf3385]

Amazing 😅 , i learn a lot of new concepts in one video , but i think i will re-watch it later , some of them seem confusing !

[@Meleeman011]

this made me rethink my web security holy shit.

[@MrVinaybhandari]

Videos are so interesting and clear with basic to advance. Keep going 😀

[@raulherbert]

Awesome explanation! Tks!

[@yeshwanth.alampalli]

Basic question 😐=> If the same origin policy blocks the request from different domain, how can cat.com make request on behalf of vulnerable.com? 🤔

[@PwnFunction]

Thats an example of Cross Origin Request, you can make requests to any website, but the response can't be read due to SOP unless the site let's you explicitly.

[@shivamyadav1283]

Is it true that SOP allows to send request cross domain but not read the responses? Why would even a request be even triggered by the browser if there is a SOP?

[@kesogonzaga2671]

4:00 how did cat.com get my session id?

[@esquilax5563]

The attacker who created cat.com never needs to know your session ID. The javascript in cat.com makes a POST request to vulnerable.com, the browser sees that it's contacting vulnerable.com, and it automatically includes the cookies (including session id)

[@dalewatson3978]

@@esquilax5563 sorry, so after i make request from vulnerable.com, and then i browsing another domain, and somehow open cat.com, the cat.com still can access my previous vulnerable.com cookies ? is it across the tab browser? what if i re-open the browser, will the request from cat.com still including the vulnerable.com cookies ? then cat.com really needs to know our history browser, so cat.com knows what was the useful cookies before ? does opening from private/incognito browser prevent csrf ?

[@esquilax5563]

​@@dalewatson3978 It goes like this: browser: hey vulnerable.com server, can you send me your content? vulnerable.com: sure, here it is, and please remember "session=123" ...later... browser: hey cat.com, can you send me your content? cat.com: sure, here it is (snigger) browser: hmm, the content says I should also ask vulnerable.com to do x, y, and z browser: hey vulnerable.com, can you do x, y, and z? And BTW you told me earlier "session=123" vulnerable.com: session ID checks out, OK, I'll go ahead and do x, y, and z. The browser knows *all* its cookies for *all* sites. When it makes a request to a site, it will only send the cookies for that site. Incognito mode can help in some cases. When you start off in incognito mode, you have no cookies, and they'll all be cleared when you close the incognito window. But you can still set cookies in the meantime. So if you're in private mode and you log into vulnerable.com, the same thing can happen. If you're only logged into vulnerable.com in your regular, non-private browser, then you can go to cat.com in private mode and this attack won't work. About closing and re-opening the browser, it all depends on when the relevant cookie is cleared. It can be set to expire when you close the browser, or to expire after a certain amount of time, or it can stay around forever. The server specifies how long the cookie should stay around when it sets the cookie. That's why many sites can decide to let you stay logged in even after the browser is closed and re-opened.

[@trishulbhuyar181]

Won’t CORS will restrict the call, when delete request initiated from cat.com to vulnerable.com ?

[@susovangarai6731]

your channel is a gold mine !!

[@kds-2049]

Explained well, props to you

[@chaosknight3175]

Ok, good stuff. Subscribed.

[@xa3da4]

I Love PwnFunction Video's ILLUSTRATION🔥🙌⚡😍

[@zxuiji]

3:49, uh but there's an origin parameter there, that means the server should be the one responsible for checking the origin has authorisation prior to carrying out any command it has sent

[@ororabrian7106]

I'm not sure about this I think that the server can decide to check this at the own descretion however this video is in the context of "what the browser does". I guess this video is about the security from the browser point of view.

[@HarujiCat]

You saved me. Thank you so much

[@chimithras4746]

Great Explanation ✅

[@a.yashwanth]

I get this as response headers but I still get the chrome cross origin error. access-control-allow-headers: Content-Type access-control-allow-origin: localhost content-length: 0 content-type: text/html; charset=UTF-8 date: Mon, 16 Mar 2020 15:52:28 GMT server: Apache status: 200

[@nolongeravailable111]

Nice video thanks for the amazing content

[@MohaDou]

That's crazy explanation, Thanks a lot

[@eLab43]

Question: Why not just use postman and set the headers? Thanks

[@ororabrian7106]

You can.... If you want to hack only yourself.

[@yuvalozeri3142]

Amazing video, so clear! thank you

[@jenniferwood4916]

Love your videos! Please make more :3

[@soufianeabbad887]

Awesome video. I hope that you explain some bugs like vulnerable flash files, JSONP and email spoofing

[@behnkenj]

Well done sir, keep them coming! :)

[@artemislwof9264]

Fucking A . i had to do couple of days of deep research to understand some of those concepts in order to have some idea about where the exploits would be . you just explained it PERFECTLY in simple terms and visuals and confirmed some of my thoughts :D . u did share some valuable and accurate information despite supid youtube terms n policies. Thank you sir for the clues XD

[@Odys42]

Awesome ! Thank you !

[@kivuosark2088]

Yes! We cannot access external website within but what about window.postMessage() ?

[@khoroshoigra8388]

most of the cases of being bypassed by other domains for a kind of request is by using */wildcard in CORS

[@timon5851]

4:08 why is cat-website allowed to send a cookie which is not his own? Where else does it now the sessionID to give a valid answer to the server? Sorry im kinda lost

[@ororabrian7106]

Sometimes it's warranted. sometimes one site depends on you being authorized on another website.

[@mitchelline]

I found a CSRF on a large website with > 500k members, so it's more common than you think! It allowed me to send their coins to my account, and those coins were bought with real money, so it was a decently critical flaw

[@karansh491]

Hey @PwnFuncrion why you're not uploading any videos now 😐

[@mk9834]

love your videos this is a god's work

[@harshitjoshi3082]

This is awesome !

[@TheShayMo1]

Hi PwnFunction , just found your channel , your animations on this video are fantastic , can you share what app you use ? Thanks & Great Job

[@PwnFunction]

Adobe animate to draw, Audacity/Auditions to edit sound and Premiere pro for editing vid.

[@kurogaming3205]

I love your videos there amazing , professional ! but I guess slow down a little bit for new people, other than that your the best I have ever being taught

[@vitorgouveia5378]

but doesn't CORS prevent this?

[@brod515]

let me get this right, if cat.com sends a request to vulnerable.com the browser automatically sends cookies of vulnerable.com with the request but cat.com can't read the response right. they crucial part is that cat.com can't read the response.

[@vanjavk]

I feel like you're correct

[@indientis6003]

*Sees **11:42* *Cries with Respect*

[@yashsodha1406]

Does the Flash CSRF JSON trick still work?

[@salahbaddou8583]

yes it does, it requires the victim to allow flash though, but it works neverthless

[@mohitpal1505]

But isn't the cookie domain-specific? When we click the cat site(evil) would it still send the cookie(containing sensitive data like sessionId), though it is not associated to hat cat's domain?

[@rulzz2581]

You are right, cookies are domain-specific. If you have two different websites opened in your browser, they will not know the Cookies of each other. But the thing is that your BROWSER knows them. And it's your browser that automatically sends them with every request to the website. Otherwise, you were supposed to re-login into the website every time you wanted to make any action.

[@LiEnby]

Wait thou the form will be sent with "Content-Type: application/x-www-form-urlencoded" and NOT "Content-Type: application/json"!!

[@ororabrian7106]

This is the problem I see with the JSON workaround as well. how do you get around this 🤷‍♂️. I'm not even sure that json data is sent in the same way form data is sent.

[@LiEnby]

@@ororabrian7106 server may not care about content type..

[@ororabrian7106]

@@LiEnby yeah that's true. alot of this is also relying on a rely lax server 😂 ... from what I've read I believe a resonable server would also look at origin and referrer

[@jimmyliu2982]

But how is it possible to post json via html form, where entry is urlencoded?

[@atharvakadlag1937]

You're videos are awesome

[@oussamasethoum1665]

Can cors prevent this request when credentials are included and the cookie is http only?

[@kaos092]

Cookies from other tabs / domains aren't sent to the server.

[@funtutes5122]

is there a video done by this guy on double submit cookies pattern?

[@585ghz]

nice video! thanks a lot!!!

[@thomaseaso]

Excellent Explanation