1 00:00:02,350 --> 00:00:04,930 So that were cross site scripting attacks, 2 00:00:04,990 --> 00:00:12,220 the most dangerous attack pattern when we talk about Javascript code. They only affect browser side Javascript 3 00:00:12,220 --> 00:00:12,630 code 4 00:00:12,670 --> 00:00:18,460 but since this is the part where you typically run a lot of Javascript code, it is a thing you definitely 5 00:00:18,460 --> 00:00:21,580 have to watch out for it and you have to be aware of. Now with that 6 00:00:21,580 --> 00:00:25,090 however, let's move on to cross site request forgery. 7 00:00:25,090 --> 00:00:26,440 What is this attack? 8 00:00:26,470 --> 00:00:32,110 It can be related to cross site scripting attacks but it doesn't have to be. The idea behind cross site 9 00:00:32,110 --> 00:00:38,980 request forgery is that people trick you into clicking on a link that leads to a prepared page where 10 00:00:38,980 --> 00:00:45,270 they abuse your local cookies to then send a request to the page you would normally talk to as well, 11 00:00:45,310 --> 00:00:47,470 let's say your online banking backend 12 00:00:47,920 --> 00:00:52,960 but since you are coming from a prepared page, you then do something there automatically without you 13 00:00:52,960 --> 00:00:58,740 recognizing that you don't want to do, for example send money to someone you don't want to send, 14 00:00:58,750 --> 00:01:03,340 maybe that even as possible to happen behind the scenes without you noticing. 15 00:01:03,340 --> 00:01:09,190 So this attack pattern also depends on injected content, so injected Javascript code but it can 16 00:01:09,190 --> 00:01:14,050 also be just HTML content which submits a form to the trusted server, 17 00:01:14,050 --> 00:01:19,510 the problem is that the form is part of an untrusted page which you might not recognize if the URL 18 00:01:19,510 --> 00:01:20,920 look similar 19 00:01:20,920 --> 00:01:26,160 and then requests on your behalf with your cookies can be made to the trustworthy server, 20 00:01:26,260 --> 00:01:30,980 so the only danger and the only problem is that this is all happening from a malicious site. 21 00:01:31,240 --> 00:01:38,110 So actions might be executed on the trustworthy page with your data without you knowing that it happens 22 00:01:38,620 --> 00:01:41,870 and therefore you might want to protect against that. 23 00:01:41,890 --> 00:01:46,630 Let's have a closer look at this pattern, though I do talk about it in more detail and also how to prevent 24 00:01:46,630 --> 00:01:46,910 it 25 00:01:47,050 --> 00:01:51,370 in my Node.js course because this is more a server side issue. 26 00:01:51,370 --> 00:01:58,890 You need to protect against CSRF attacks on the server side by using a mechanism which is a CSRF token 27 00:01:58,960 --> 00:02:05,080 and again I do discuss this in my Node.js course where we work on the server side on the backend all 28 00:02:05,080 --> 00:02:06,070 the time. 29 00:02:06,070 --> 00:02:09,410 So CSRF stands for cross site request forgery 30 00:02:09,430 --> 00:02:14,350 and the idea is that if you're the user of a web app and you have some backend, let's say the online 31 00:02:14,350 --> 00:02:18,440 banking site which uses Node.js or any other programming language, 32 00:02:18,460 --> 00:02:25,390 this is not exclusive to Javascript, uses any programming language and it talks to database, the server. 33 00:02:25,390 --> 00:02:28,540 Now you are visiting the frontend of this page, 34 00:02:28,540 --> 00:02:34,450 let's say that the user interface of your online banking site and now when you have such a setup, typically 35 00:02:34,450 --> 00:02:38,590 the server-side application identifies you with a so-called session, 36 00:02:38,590 --> 00:02:44,170 so you logged in and then the server side generates this session object, stores session data on the 37 00:02:44,170 --> 00:02:47,950 server and sends you the session ID which is stored in a cookie, 38 00:02:47,950 --> 00:02:54,800 that's a typical authentication setup you have in web pages where frontend and backend work together. 39 00:02:54,820 --> 00:03:00,560 Now then you might be sending an intended request, for example to send money to be and all is good. 40 00:03:00,580 --> 00:03:06,580 The problem is that if you now visit a fake site because someone sends you a link to it, which looks 41 00:03:06,580 --> 00:03:15,310 like the trustworthy site but which isn't, then you visit this page and there, people send a request to 42 00:03:15,310 --> 00:03:21,700 the trustworthy backend, therefore the browser attaches cookies that belong to this trustworthy backend 43 00:03:21,850 --> 00:03:25,480 which is your session ID for example and everything works. 44 00:03:25,480 --> 00:03:31,600 The problem just is since you're on a fake site, the request might be one that is intended by the fake site 45 00:03:31,630 --> 00:03:38,620 but not by you, for example to send money to C and this request will succeed because you sent the right 46 00:03:38,620 --> 00:03:42,880 cookie, the right session ID and you sent it through the right backend. 47 00:03:42,910 --> 00:03:45,840 So again more details can be found in a Node.js course 48 00:03:45,850 --> 00:03:51,070 but this is also a potential tech pattern but not directly linked to Javascript. 49 00:03:51,070 --> 00:03:56,530 It can be implemented with cross site scripting attacks but it can also be implemented by using such 50 00:03:56,530 --> 00:04:00,290 a fake site which does not require cross site scripting attacks. 51 00:04:00,370 --> 00:04:04,530 So therefore this is not really a Javascript security thing, 52 00:04:04,600 --> 00:04:08,440 it's more a server side or general web application security thing 53 00:04:08,440 --> 00:04:13,600 and therefore I do discuss it in more detail in my Node.js course where we write a lot of server side 54 00:04:13,600 --> 00:04:13,990 code.