Full Report
A little while back we published our first public QoW for your abuse and enjoyment, and the time to close it is ………. now. The new QoW is available here. Thanks for the efforts; we received a fair number of answers and are still figuring out how to go about recording your submissions. For now, we’ll publish the first correct answer, and discuss the answer in brief. Over to Haroon: Jeremiah Grossman was the first correct answer, with valiant attempts from many others.. Acceptable solutions involved either the use of JavaScript / HTML comments to allow our injection to span multiple lines (or really really small urls :>)
Analysis Summary
The provided article describes the solution to a previous "Question of the Week" (QoW) challenge posed by SensePost in July 2007, focusing on an injection technique rather than a specific malware family or complex attack framework. The technique centers on exploiting how a particular web application handled input parameters to execute arbitrary JavaScript.
Here is the summary structured according to your requirements:
# Tool/Technique: JavaScript/HTML Comment Injection for Command String Construction
## Overview
This technique involves abusing the input handling mechanism of a web application (likely a CGI script handling GET requests) by using JavaScript and HTML/URL comments (`/*` and `*/`) to fragment a malicious JavaScript command across multiple, seemingly benign `name=value` pairs in a URL query string. The fragments are reassembled and executed via `eval()`.
## Technical Details
- Type: Technique
- Platform: Web Application (Client-side via injected script execution in a browser)
- Capabilities: Bypassing input length restrictions or obfuscating malicious code by spreading it across controllable input fields.
- First Seen: Contextually associated with the challenge published around July 2007.
## MITRE ATT&CK Mapping
This technique primarily maps to execution and obfuscation:
- **TA0002 - Execution**
- **T1059 - Command and Scripting Interpreter**
- **T1059.001 - Command and Scripting Interpreter: PowerShell** (If the payload was targeting PowerShell, but here it is JavaScript)
- **T1059.007 - Command and Scripting Interpreter: JavaScript** (Most relevant for the client-side payload)
- **TA0005 - Defense Evasion**
- **T1027 - Obfuscated Files or Information** (Via code fragmentation across hidden parameters)
## Functionality
### Core Capabilities
- **Bypassing Length Constraints:** Utilizing multi-line comments (`/* ... */`) to allow the JavaScript string components to span across multiple assigned parameters (`name=value` pairs).
- **Code Fragmentation:** Breaking a full malicious command (`document.location=...`) into smaller, distinct strings (`a`, `b`, `c`, `d`, `f`).
- **Dynamic Reassembly:** Using string concatenation within the injected code structure to rebuild the final command.
### Advanced Features
- **Use of `eval()`:** Employing the `eval()` function to execute the dynamically concatenated string as code, thereby achieving code execution from fragmented input.
- **Targeted Action:** In the example, the goal was to change `document.location` to redirect the user, but the attacker notes "the world is your oyster," suggesting arbitrary client-side code execution was possible.
## Indicators of Compromise
Since this is a description of a technique used in a specific challenge, concrete IOCs are abstract:
- File Hashes: N/A (Client-side execution via request parameters)
- File Names: N/A
- Registry Keys: N/A
- Network Indicators: The example payload attempted to build a URL using parts that included a defanged IP address in the URL construction logic: `168.210.134.1`.
- Behavioral Indicators: Observation of unexpected data being passed across multiple seemingly unrelated form parameters designed to construct a single executable JavaScript string.
## Associated Threat Actors
- No specific threat actor group is mentioned; this was a vulnerability/technique demonstrated in a public challenge by SensePost.
## Detection Methods
- Signature-based detection: Signatures looking for the specific sequence of input parameters combined with comment structures used to build an HTTP request URL intended for injection.
- Behavioral detection: Monitoring HTTP requests for parameters containing fragmented JavaScript syntax (`/*`, `*/`, chained string assignments, followed by a final `eval()` or similar execution attempt).
- Yara rules: Not directly applicable to the request itself, but server-side logic scanning for this structure in incoming requests might apply.
## Mitigation Strategies
- **Input Validation & Sanitization:** Strictly sanitize or reject input containing comment delimiters (`/*`, `*/`) or known code execution keywords (`eval`, `document.location`, etc.) if they are not expected in standard input fields.
- **Use of Safe APIs:** Avoid reflecting raw user input directly into JavaScript contexts without strict encoding.
- **Output Encoding:** Ensure all user-supplied values reflected into HTML or JavaScript contexts are properly encoded for that context (e.g., encoding `"` or `'` characters appropriately).
## Related Tools/Techniques
- Standard JavaScript Injection techniques.
- Polyglot input development (though less complex than typical polyglot use).
- Input fragmentation/obfuscation techniques used to bypass basic Web Application Firewalls (WAFs).