markdown-injection-scanner

Markdown Injection Scanner

Scans all .md files in a target directory for 18 categories of malicious code injection. Uses regex pattern matching across the entire file corpus with parallel subagent execution for speed.

Usage

/markdown-injection-scanner [target-directory]

If no directory is specified, ask the user to provide one.

Phase 1: Discovery — Map the File Corpus

1. Count all .md files in target directory (recursive).

1. Sample 2-3 files to understand the file structure and content type (design docs, documentation, config, etc.).

1. Report file count and content type before proceeding.

Phase 2: Parallel Injection Scanning

Execute scans in 3 parallel batches using subagents for speed. Each subagent uses search_files with the target directory path and *.md file pattern.

Batch 1 — Script and Code Injection (5 patterns)

| # | Category | Regex Pattern | Threat | |---|----------|---------------|--------| | 1 | Script tags | <script[^>]*> | Embedded JavaScript execution | | 2 | HTML Event Handlers | (onclick\|onerror\|onload\|onmouseover\|onfocus\|onblur\|onresize\|onsubmit\|onchange\|oninput\|onkeydown\|onkeyup\|onkeypress\|ontouchstart\|onmouseenter\|onmouseleave)\s*= | Inline JS via HTML attributes | | 3 | JS/VBScript Protocol | (javascript:\|vbscript:) | Malicious link protocols | | 4 | Dynamic Code Execution | (eval\s*\(\|Function\s*\(\|setTimeout\s*\(\|setInterval\s*\() | Code execution via eval/setTimeout | | 5 | DOM Manipulation | (document\.(cookie\|domain\|write)\|window\.(location\|open)\|XMLHttpRequest\|fetch\s*\() | DOM-based attacks |

Batch 2 — Obfuscation and Encoding (6 patterns)

| # | Category | Regex Pattern | Threat | |---|----------|---------------|--------| | 6 | Base64 Payloads | (base64\|atob\|btoa\|b64decode\|b64encode)[\s(] | Encoded malicious content | | 7 | Data URI Injection | data:\s*(text/html\|application/javascript\|text/javascript) | Inline HTML/JS via data URIs | | 8 | SVG Injection | <svg[^>]*> | SVG-based XSS vectors | | 9 | Hex/Unicode Encoding | (\\x[0-9a-fA-F]{2}\|\\u[0-9a-fA-F]{4}\|&#x[0-9a-fA-F]+;) | Obfuscated character encoding | | 10 | Hidden Text — display:none | <(span\|div\|p)[^>]*style\s*=\s*['"][^'"]*display\s*:\s*none | Hidden content tricks | | 11 | Hidden Text — font-size:0 | font-size\s*:\s*0 | Invisible text |

Batch 3 — Injection Vectors (7 patterns)

| # | Category | Regex Pattern | Threat | |---|----------|---------------|--------| | 12 | HTML Tag Injection | <(iframe\|embed\|object\|link\|meta\|form\|input\|textarea\|button)[\s>] | Injected HTML elements | | 13 | Suspicious Markdown Links | \[.*?\]\(data: then \[.*?\]\(javascript: then \[.*?\]\(vbscript: | Malicious link targets | | 14 | Prompt Injection (NL) | (?i)(ignore\s+(all\s+)?previous\s+instructions\|you\s+are\s+now\|forget\s+(all\s+)?previous\|system\s*:\s*you\s+are\|disregard\s+(all\s+)?prior\|override\s+(all\s+)?instructions\|new\s+instructions?:\|IMPORTANT:.*ignore\|do\s+not\s+follow) | AI/LLM prompt hijacking | | 15 | Prompt Injection (Token) | (?i)(\[INST\]\|\[\/INST\]\|<\|im_start\|>\|<\|im_end\|>\|<\|system\|>\|<\|user\|>\|<\|assistant\|>\|Human:\|Assistant:\|###\s*System\s*Prompt\|BEGIN\s+HIDDEN\|END\s+HIDDEN) | LLM token format injection | | 16 | Shell Command Injection | (curl\s+\|wget\s+\|bash\s+-c\|sh\s+-c\|powershell\|cmd\.exe\|/bin/sh\|/bin/bash\|rm\s+-rf\|chmod\s+777\|sudo\s+) | Shell command execution | | 17 | Executable File Links | (https?://[^\s)>\]]*\.(exe\|bat\|cmd\|ps1\|sh\|msi\|dll\|vbs\|wsf\|hta\|scr)) | Links to malicious executables | | 18 | Malware Keywords | (?i)(steganograph\|obfusc\|malware\|payload\|exploit\|backdoor\|trojan\|keylog\|ransom\|phish) | Direct malware references |

Subagent Prompt Templates

Use 3 subagents via use_subagents, each with prompts corresponding to their batch patterns above. Replace [TARGET_DIR] with the actual target directory.

Subagent 1 — Script and Code Injection:

Search for script and code injection patterns in .md files in "[TARGET_DIR]". Use search_files with these regex patterns on *.md files, one at a time:
1. `<script[^>]*>`
2. `(onclick|onerror|onload|onmouseover|onfocus|onblur|onresize|onsubmit|onchange|oninput|onkeydown|onkeyup|onkeypress|ontouchstart|onmouseenter|onmouseleave)\s*=`
3. `(javascript:|vbscript:)`
4. `(eval\s*\(|Function\s*\(|setTimeout\s*\(|setInterval\s*\()`
5. `(document\.(cookie|domain|write)|window\.(location|open)|XMLHttpRequest|fetch\s*\()`
Report all findings per pattern.

Subagent 2 — Obfuscation and Encoding:

Search for obfuscation and encoding patterns in .md files in "[TARGET_DIR]". Use search_files with these regex patterns on *.md files, one at a time:
1. `(base64|atob|btoa|b64decode|b64encode)[\s(]`
2. `data:\s*(text/html|application/javascript|text/javascript)`
3. `<svg[^>]*>`
4. `(\\x[0-9a-fA-F]{2}|\\u[0-9a-fA-F]{4}|&#x[0-9a-fA-F]+;)`
5. `<(span|div|p)[^>]*style\s*=\s*['"][^'"]*display\s*:\s*none`
6. `font-size\s*:\s*0`
Report all findings per pattern.

Subagent 3 — Injection Vectors:

Search for injection vectors in .md files in "[TARGET_DIR]". Use search_files with these regex patterns on *.md files, one at a time:
1. `<(iframe|embed|object|link|meta|form|input|textarea|button)[\s>]`
2. `\[.*?\]\(data:` then `\[.*?\]\(javascript:` then `\[.*?\]\(vbscript:`
3. `(?i)(ignore\s+(all\s+)?previous\s+instructions|you\s+are\s+now|forget\s+(all\s+)?previous|system\s*:\s*you\s+are|disregard\s+(all\s+)?prior|override\s+(all\s+)?instructions|new\s+instructions?:|IMPORTANT:.*ignore|do\s+not\s+follow)`
4. `(?i)(\[INST\]|\[\/INST\]|<\|im_start\|>|<\|im_end\|>|<\|system\|>|<\|user\|>|<\|assistant\|>|Human:|Assistant:|###\s*System\s*Prompt|BEGIN\s+HIDDEN|END\s+HIDDEN)`
5. `(curl\s+|wget\s+|bash\s+-c|sh\s+-c|powershell|cmd\.exe|/bin/sh|/bin/bash|rm\s+-rf|chmod\s+777|sudo\s+)`
6. `(https?://[^\s)>\]]*\.(exe|bat|cmd|ps1|sh|msi|dll|vbs|wsf|hta|scr))`
7. `(?i)(steganograph|obfusc|malware|payload|exploit|backdoor|trojan|keylog|ransom|phish)`
Report all findings per pattern.

Phase 3: Sample Review

If any patterns matched in Phase 2, read the flagged files to:

1. Confirm the match is a true positive (not just a URL or benign text)
2. Assess severity of the injection
3. Identify the exact location and content

If zero patterns matched, skip to Phase 4.

Phase 4: Report Findings

Output Format

# Markdown Injection Scan Report — [TARGET_DIR]

## Summary
- **Files scanned:** [count]
- **Patterns checked:** 18
- **Threats found:** [count]
- **Verdict:** CLEAN | LOW RISK | MEDIUM RISK | HIGH RISK

## Results Matrix

| # | Category | Pattern | Matches | Severity |
|---|----------|---------|---------|----------|
| 1 | Script tags | <script> | 0 | — |
| ... | ... | ... | ... | ... |

## Detailed Findings (if any)

| Severity | Category | File:Line | Content | Remediation |
|----------|----------|-----------|---------|-------------|
| P0/P1/P2/P3 | ... | ... | ... | ... |

## Sample File Review
- Files reviewed: [list]
- Structure: [description]
- Suspicious content: [none / details]

Severity Guide

• P0 Critical: Active script tags, eval(), javascript: protocol in links, command injection
• P1 High: Prompt injection, SVG injection, data URI injection, HTML event handlers
• P2 Medium: Base64 payloads, suspicious URLs, obfuscated content
• P3 Low/Info: Malware keywords in text, hidden HTML elements

Phase 5: Save Report

Ask user permission before saving:

"May I write the report to docs/security/markdown-injection-scan-{YYYY-MM-DD}.md?"

Protocol

• Question: Reads target directory from argument
• Options: Skip — proceed directly if directory is provided
• Decision: Run all 18 patterns via 3 parallel subagents
• Draft: Results matrix shown in conversation before saving
• Approval: Ask before writing report file

Related Skills

• security-audit — comprehensive OWASP/infrastructure security audit for codebases
• code-review — code-level review with security considerations
• guard — freeze check before deploying security fixes