HTML (HyperText Markup Language) is a language used to create web pages using tags inline with the content to indicate to browsers how to display that content, using the tags to interpret formatting, images, scripts and other content.

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79
votes
5answers
38k views

Should websites be allowed to disable autocomplete on forms or fields?

Currently, there is an HTML form/input attribute called autocomplete, which, when set to off, disables autocomplete/autofill for that form or element. Some banks seem to use this to prevent password ...
58
votes
1answer
3k views

“Allow __ to be fullscreen?”

I have been asking myself for a while what's the purpose of that popup showing up in pretty much all the modern browsers upon entering the full-screen mode of a video or website. It appears to be a ...
57
votes
6answers
9k views

Anonymous surveys that aren't so anonymous

In the past I have completed an 'anonymous' survey at work only to find that my employer was able to garner a lot of not-anonymous information from this survey. Location, name of manager, etc. None ...
40
votes
4answers
6k views

Have computer criminals been known to exploit easily-edited websites like Wikipedia to embed malicious scripts?

When I was reading a page on Wikipedia several months ago (December 2014) I saw what looked like a pop-up window from BT, but I soon realized that when I closed the page the pop-up disappeared. I then ...
21
votes
2answers
2k views

Does this CSS code expose if a message is read, and how long they have been reading it?

This email analytics company offers an 'engagement metric' that shows how much time someone spends looking at an email, whether the email is printed or deleted. They also claim it works in pretty ...
14
votes
3answers
1k views

What does a HTML filter need to do, to protect against SVG attacks?

I recently learned that SVG (Scalable Vector Graphics) images introduce a number of opportunities for subtle attacks on the web. (See paper below.) While SVG images may look like an image, the file ...
13
votes
1answer
995 views

How can I embed iframe securely without restricting its functionality?

I'd want to embed an iframe from untrusted site into web application. Iframe: should be able to run Javascript and browser plugins (Flash, etc.) should not be able to access my web application ...
11
votes
2answers
2k views

Attack Vectors for Purely Static Website (HTML and CSS)

I am sorry if this is a too trivial question, but once I was told that only a fool is sure of anything: as I am not sure about this question, I am willing to risk my neck by asking it anyway, all in ...
10
votes
2answers
2k views

How do the Stack Exchange sites protect themselves from XSS? [duplicate]

It seems to me that because Users can post questions and comments in them with HTML markup (possibly <script> tags), Stack Exchange sites would be very exposed to XSS attacks. How do they ...
10
votes
2answers
3k views

How to launch XSS code from an INPUT HTML tag upon page load?

Say I have the a website with the following code on it: <input type="text" id="search-text" name="query" value="?" /> Double quotes aren't escaped so I can break out of the value attribute, ...
10
votes
3answers
3k views

Allowing users to input a safe subset of HTML

I recently posted this question on Code Review and it was recommended that I ask you guys about it. Basically, this will be used to allow users to generate formatted content. It gets put inside of ...
10
votes
1answer
434 views

Should Content in <noscript> Blocks Be Escaped

The title pretty much says it all. It seems counter-intuitive to escape inside a <noscript> block because any js that an attacker is able to inject there shouldn't be executed. But, I'm still ...
9
votes
3answers
5k views

Is there a way to bypass Django's XSS escaping with “unicode”?

Django (the Python web framework) escapes output to prevent XSS (Cross Site Scripting) attacks. It replaces ', ", <, >, & with their HTML safe versions. However this presentation on slide ...
9
votes
2answers
150 views

Best practices when forwarding an email or copy / pasting from confidential information sources?

I get asked this a lot from older people, or for legal matters. They want to forward an email message they've received to another party, while removing any identifying information from the first party ...
9
votes
3answers
961 views

Any eventhandlers that apply to hidden elements?

I'm trying to XSS a search field and my attack vector is getting reflected like this: <input type="text" id="txtRpHiddenKeyword" style="display: none;" value="ATTACK VECTOR HERE" /> Only ...
8
votes
1answer
2k views

What are the benefits and drawbacks of the HTML5 Keygen element?

As of January 2013, what are the potential benefits and drawbacks of the HTML5 Keygen element?
8
votes
3answers
989 views

Is a HTML form tag more exploitable than a HTML link in user submitted content?

I have a content editor in a web application which allows administrators to add and edit content in certain areas of the application. The editor component I have used automatically removes any script ...
7
votes
6answers
1k views

Cleartext password in HTML

Is there any problem with outputing a user's password to the HTML in an hidden field (see use case below before flaming xD)? The use case is a registration form with two steps. The user fills in the ...
7
votes
1answer
2k views

What possible use does an iFrame have for security?

I'm looking at code for an old login form I'm redesigning. It's a simple table with two input fields for username and password. But just before the end </table> tag there's a blank iFrame which ...
7
votes
4answers
357 views

Limited JavaScript app scenario: Attack vectors and mitigation

I'm going to be developing a single page JavaScript app which allows input via a textarea. This input is never sent to the server, never shown to another user, and will only be persisted in browser ...
7
votes
1answer
369 views

Safe to render data directly to DOM from localStorage? XSS attack possible?

I read that localstorage is susceptible to XSS attacks. I currently store JSON Web Token (JWT) in localstorage, and I access and display data about the user through localstorage: var localstore = //...
7
votes
2answers
1k views

Drupal filters XSS with regexes. What could bypass it?

Drupal filters HTML strings against XSS attacks using regexes: http://api.drupal.org/api/drupal/includes%21common.inc/function/filter_xss/7 However, as a lot of people know, HTML can't be parsed with ...
6
votes
4answers
10k views

how can you inject malicious code into an innocent-looking URL?

I am learning about XSS attacks. Wikipedia says that in a non-persistent attack an attacker may provide an innocent-looking URL that "points to a trusted site but actually has an XSS vector." What ...
6
votes
2answers
1k views

Escaping rich text editor output

When having a rich text editor on a web application, what is the best way to escape HTML entities and prevent XSS attacks but keep the formatting (<b>, <i>, <u>, ...etc.) ?
6
votes
2answers
848 views

Workarounds for :visited CSS History reconnaissance

Several years ago it was possible to use a:visited { background: url('/log.php'); } to figure out on what website user has been previously. But now it is restricted by browsers. Is there any ...
6
votes
1answer
322 views

How do I securely embed an <img> tag using a user-given URL?

If I hypothetically wanted to allow users to use an avatar from an arbitrary URL like this: <img class="avatar" src="{user input}" /> There are many problems that I can think of: There are ...
5
votes
4answers
2k views

Is it possible to make an xss with only html tags

I'm not aware of all the xss tricks.. While programming in Ruby on Rails, using a sanitize method to allow only certain tags and it makes its best to clear all the other tags and scripts the ...
5
votes
4answers
1k views

Is this an attack and how can I fix it?

I don't know where to start in searching the forum for existing threads that might cover my issues. I recently received a spoof email pretending to be from a client for whom I've just started to do ...
5
votes
2answers
797 views

Should every output element be filtered, or just those which contain user-editable data? [duplicate]

I'm combing through a legacy app updating SQL to prevent Injections and XSS vulnerabilities. I know to apply PHP's htmlspecialchars() anything that is directly passed to a script and displayed on a ...
5
votes
5answers
1k views

HTML Entities to hide Email Addresses

I'm on WordPress trying to keep spambots from grabbing email addresses that may be in The Content. WordPress has a nifty little function simply called antispambot() which will convert the email ...
5
votes
3answers
123 views

Input validation: how to do it if I must accept HTML as part of my input?

I'm writing a service which receives FHIR data and it stores it. FHIR is an HL7 healthcare information standard format which contains HTML by definition, embedded into a JSON or XML, (to ensure human-...
5
votes
1answer
54 views

Why don't web templating frameworks HTML escape all data by default?

I recently discovered an XSS vulnerability in an application that uses JSP to render pages. The vulnerable code in the JSP was something like this: <td>${customer.notes}</td> It was ...
5
votes
1answer
609 views

Why is a child window allowed to change the location of its parent?

Maybe a silly question. When opening a new tab via target="_blank", the page that loads in that tab is allowed to set a new location in the parent tab using: window.opener.location.replace('http://...
5
votes
4answers
79 views

Would an official <disablescripts> HTML (6?) element/wrapper combat XSS effectively?

Would it not be possible to use such a method to wrap areas where user input/output is expected (eg. comment boxes), so that even if a script is successfully injected through regex evasion, the script ...
5
votes
2answers
976 views

Closing an HTML tag without using the actual character

I'm currently learning how to perform XSS on websites, but there is a constant problem that keeps recurring that I'm sure must be easy to bypass. Quite often, the website will filter out quotation ...
5
votes
5answers
2k views

Sharing Nmap scan results in a web page [closed]

Is there a tool that allow the sharing of nmap scan results ? I know nmap can produce XML and I can easily convert them in HTML. I would like to know if there is a tool with more features. For ...
4
votes
3answers
7k views

Is it possible for a hacker to bypass upload php file?

I wanna give a filtering system in my script. here it is : <?php $allowedExts = array("gif", "jpeg", "jpg", "png","bmp"); $temp = explode(".", $_FILES["file"]["name"]); $extension = end($temp); ...
4
votes
1answer
39 views

table elements are not encrypted

I read a security book a while ago that said HTML table elements are sent plain text, even if the server connection is https. Is this accurate? I'm thinking about making an on-line purchase from a ...
4
votes
2answers
234 views

To What Extent does an Attacker Have Access to the Browser History through the CSS Pseudoclass :visited Styles?

I have read this article on how a scripted web page is able to obtain the visited history of a user browsing the page. However, I can't find any clear information in the article describing the extent ...
4
votes
2answers
6k views

Why are scripts injected through innerHTML not executed whilst onerror and other on<event> attributes on elements are? - Google XSS Challenge 2

SPOILER ALERT : Do not continue if you do not want to be spoiled I am currently doing the Google XSS Challenge Level 2 . I am injecting XSS code that is inserted into the document using element....
4
votes
3answers
3k views

Content-Security-Policy hash of script

<?php header("Content-Security-Policy: default-src 'sha256-".base64_encode(hash('sha256', 'console.log("Hello world");', true))."'"); ?> <script>console.log("Hello world");</script> ...
4
votes
1answer
2k views

OWASP Recommendation on Client-Side Password Hashing

The OWASP Application Security FAQ recommends the use of JavaScript to produce a salted hash of the password client-side with JavaScript prior to sending it to the server. Is this something truly ...
4
votes
1answer
122 views

Risks of HTML/JavaScript window.opener security flaw?

I do not know if you are aware of this flaw, but here is a basic example: somepage.html (pointing to malicious.html): <!DOCTYPE html> <html> <head> <meta charset="utf-8"> ...
3
votes
2answers
984 views

Set the max length for input

Suppose I have a form, and one of this form inputs I set the max length to 15: <input type="text" name="username" maxlength="15"> Now the attacker wants to override this limit, to do that he ...
3
votes
5answers
3k views

Is converting `<` to `&lt;` sufficient to prevent execution of JavaScript from arbitrary HTML?

This is kind of a bar-bet question. An acquaintance of mine has made the claim that, given an arbitrary glob of HTML, it can be completely prevented from executing JavaScript if, before slapping it ...
3
votes
5answers
2k views

Is it secure to use jQuery on the server-side for user input validation?

I'm thinking about using jQuery on the server-side (node.js) to validate user input (filter tags, remove every attributes except href, rel, target & style, modify css rules which are applied ...
3
votes
3answers
712 views

Stop code injections into page code

I started a topic HERE on the stackoverflow site, but was refered here. I did get some info there, but think it need's more indepth input. So hopefuly people here can help. I have a few domains ...
3
votes
1answer
151 views

Browser exploits based purely on HTML + CSS

In 2011, Eli Fox-Epstein demonstrated a Rule 110 machine in HTML + CSS3. This led some to say that the combination of HTML + CSS3 is Turing complete. Regardless of whether HTML + CSS3 is technically ...
3
votes
3answers
293 views

Any Security Risks for using mailto:?

I use a PHP script which performs a database search and when no result are found, user is presented with a mailto link with this format mailto:example@test.com?subject=SEARCHED_QUERY_HERE The ...
3
votes
3answers
616 views

OWASP escaping recommendation - why /?

In OWASP recommendations regarding escaping untrusted input for HTML element content, they list the following: & --> &amp; < --> &lt; > --> &gt; " --> &quot; ' --...