👉 Overview
👀 What ?
Dangling Markup, also known as HTML scriptless injection, is a technique used in cyber attacks to exploit vulnerabilities in a website or application's HTML code. This technique involves injecting malicious content into the HTML code, without using any scripts, hence the term 'scriptless'. This content could, for instance, alter the webpage's behaviour or layout, or be used to steal sensitive user information.
🧐 Why ?
Understanding Dangling Markup is crucial for both developers and cybersecurity professionals. For developers, this knowledge can help prevent potential vulnerabilities in their HTML code. For cybersecurity professionals, it can assist in identifying and mitigating attacks. Given the rise in web-based applications and services, such attacks can pose a significant threat to data privacy and security.
⛏️ How ?
Dangling Markup works by taking advantage of unquoted attributes in HTML tags. The attacker injects additional attributes or changes the existing ones, altering the webpage's behaviour. For instance, the attacker could inject a link that redirects users to a malicious website. To prevent such attacks, always quote your attributes and sanitize user inputs. Also, use security headers like Content Security Policy (CSP), which can prevent the loading of malicious content.
⏳ When ?
Dangling Markup attacks have been around for quite some time. However, they gained more attention in the late 2000s when web applications became more prevalent. Nowadays, with the rise in sophisticated cyber attacks, understanding and preventing such attacks is more important than ever.
⚙️ Technical Explanations
In a Dangling Markup attack, the attacker injects malicious content into the HTML code. This is usually done by taking advantage of unquoted attributes in HTML tags. For instance, consider an HTML tag with an unquoted href attribute: <a href=http://example.com>. An attacker could inject additional attributes to this tag, such as: <a href=http://example.com onmouseover=malicious_code>. Now, whenever the user hovers over this link, the malicious code will be executed. This could lead to various negative outcomes, such as data theft or website defacement. To prevent such attacks, always quote your attributes (e.g., <a href='http://example.com'>) and sanitize user inputs. Moreover, use security headers like Content Security Policy (CSP), which can prevent the loading of malicious content.