HTML (HyperText Markup Language) is a language used to created web pages.

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56
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 ...
53
votes
4answers
22k 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 ...
21
votes
2answers
1k 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 ...
13
votes
3answers
879 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 ...
10
votes
1answer
310 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 ...
10
votes
1answer
809 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 ...
9
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 ...
9
votes
3answers
4k 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 ...
8
votes
3answers
2k 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 ...
8
votes
2answers
1k 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 ...
7
votes
6answers
805 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
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?
7
votes
4answers
298 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
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 ...
5
votes
2answers
772 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
2answers
783 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.) ?
5
votes
2answers
704 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 ...
5
votes
1answer
150 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 about: There ...
5
votes
1answer
207 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: ...
5
votes
2answers
674 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
1k 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 ...
5
votes
2answers
357 views

Any eventhandlers that apply to hidden elements?

Im 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 ...
4
votes
4answers
1k 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 ...
4
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 ...
4
votes
5answers
882 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 ...
4
votes
3answers
4k 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
2answers
162 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
3answers
3k 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 ...
4
votes
1answer
1k 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
126 views

What are some useful tags and payloads for HTML injection on CSP-protected sites?

I'm pen-testing a website that fixed most of its XSS vulnerabilities by just adding a Content Security Policy. There are still HTML injections in several places. I've tried to get a ...
4
votes
3answers
1k 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> ...
3
votes
2answers
454 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
4answers
5k 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 ...
3
votes
5answers
1k 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
647 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
3answers
96 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
2answers
383 views

Injecting information in a web page (Gmail). Does it raise security problem?

I am developing a Google Chrome extension which encrypts/decrypts emails for Gmail users. So, I detect encrypted emails when the user opens an email on using tags. Once an encrypted email has been ...
3
votes
3answers
124 views

Why did I see an insecure browser warning on my page?

Originally I was under the impression that a particular page on a site I visited was showing an insecure content warning in my browsers due to the tags on the page having plan http href attributes. ...
3
votes
1answer
235 views

Danger of hidden html form uploading users local files without their knowledge

Is there a danger that a webpage could have a hidden form with a file upload input and js script that would try and take a random guesses at files on a users system and attach them to the form and ...
3
votes
1answer
580 views

How can I check the iframe on my website is secure or not?

My website has an iframe used for loading my client's websites (only 5).How can I make sure the iframe is secure? Also by editing iframe src It allows to load any other websites.How can I prevent it?
3
votes
1answer
176 views

How can I successfully perform an xss attack on a dummy website? [closed]

in my security course, we were told to practice an xss attack using firefox on this website; http://permalink.co/ No worries, this is a website specifically setup for us to practice ...
3
votes
1answer
87 views

What methods can be used to prevent the browser (IE11 specifically) from storing credentials / autocomplete

Going through Pen Test and it was asked of us to disable auto complete in our CC payment fields. We tried adding autocomplete=off and also tried false on the input filed. A ny suggestions to ...
2
votes
4answers
387 views

Clickjacking: can't browsers just forbid/reject placing transparent elements over frames?

Why not? Seems like this is only used for clickjacking, the solution should be simple enough.
2
votes
4answers
1k views

Simple solution to XSS

I've got an idea as to how to defeat XSS so simple that it may work and was wondering if anybody had already done something similar. The goal here is not efficiency but security. In other words I ...
2
votes
5answers
1k 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 ...
2
votes
3answers
2k views

Javascript containing a long hexadecimal string and eval: is this suspicious?

At the bottom of the index.php file for a simple “contact us” form, I found the following (some whitespace and newlines added): try {if(window.document)--document.getElementById('12')} catch(qq) ...
2
votes
2answers
173 views

is it sufficient to convert '(single-quote) to ` &#039; `

Is it sufficient to convert ' to &#039; , > converted to &gt; and < converted to &lt; to avoid xss A bit of context: the payload would be going through the URL and landing in a ...
2
votes
3answers
387 views

OWASP escaping recommendation - why /?

In OWASP recommendations regarding escaping untrusted input for HTML element content, they list the following: & --> &amp; < --> &lt; > --> &gt; " --> &quot; ' ...
2
votes
1answer
141 views

Exploiting mailto links

Supposing that the user has the power to include any content after mailto: snippet, are there any possible security vulnerabilities? Example: The user says their email address is foo. The link on ...