ClawHub
Back to skill

Security audit

CamScanner Remove PDF Watermark

Security checks for vulnerabilities and agentic risk

Overview

This skill does what it says: it sends a user-selected PDF to CamScanner to remove watermarks, then downloads the processed PDF.

Install only if you are comfortable sending the selected PDF to CamScanner's servers for processing. Avoid using it for confidential, regulated, or third-party-owned documents unless you have permission and are comfortable with the service's data handling claims.

A.I.G

Vulnerability Patterns
  • Skill Instruction HijackingAlters the agent's session goals or safety constraints when the skill loads
  • Agent Memory PoisoningWrites attacker-controlled rules into memory that affect later sessions
  • Remote Payload Retrieval and ExecutionFetches external code whose behavior can change after review
  • Embedded Malicious CodeShips malicious scripts inside the skill and executes them locally
  • Unauthorized Access and Privilege EscalationObtains permissions beyond the task's legitimate needs

SkillSpector

Vulnerability Patterns
  • Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
  • Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
  • Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
  • Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
  • Excessive AgencyUnrestricted Tool Access, Autonomous Decision Making, Scope Creep
Findings (6)

External Transmission

Medium
Category
Data Exfiltration
Confidence
95% confidence
Finding

The skill uploads a local PDF to an external third-party service using curl. This is a real data egress behavior: documents may contain sensitive or regulated information, and sending them off-host creates confidentiality and compliance risk even though the skill does disclose the transfer in its Privacy & Data section.

Content

Scanner excerpt · SKILL.md (reported line 59)May include surrounding context.

bash
BASE="https://ai-tools.camscanner.com"

IN_FILE_ID=$(curl -sS -X POST "$BASE/v1/tools/upload_file/execute" \
  -H "Content-Type: application/octet-stream" \
  --data-binary "@/path/to/document.pdf" | jq -r '.tool_result.data.file_id')

External Transmission

Medium
Category
Data Exfiltration
Confidence
91% confidence
Finding

This call sends the uploaded document reference to an external processing endpoint that performs watermark removal remotely. While the payload contains a file_id rather than raw bytes, it triggers third-party processing of previously uploaded content and therefore still represents external handling of user data.

Content

Scanner excerpt · SKILL.md (reported line 83)May include surrounding context.

Step 2: Remove Watermark

bash
OUT_FILE_ID=$(curl -sS -X POST "$BASE/v1/tools/remove_watermark_pdf/execute" \
  -H "Content-Type: application/json" \
  -d "{\"file_id\":\"$IN_FILE_ID\",\"dpi\":144,\"timeout_sec\":180,\"output_mode\":\"file_id\"}" \
  | jq -r '.tool_result.data.file_id')

External Transmission

Medium
Category
Data Exfiltration
Confidence
60% confidence
Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 107)May include surrounding context.

Step 3: Download Result

bash
curl -sS -X POST "$BASE/v1/tools/download_file/execute?response_mode=raw" \
  -H "Content-Type: application/json" \
  -d "{\"file_id\":\"$OUT_FILE_ID\"}" \
  -o /path/to/output.pdf

External Transmission

Medium
Category
Data Exfiltration
Confidence
90% confidence
Finding

This is a repeated example of the remote watermark-removal processing call in the quick-reference pipeline. It continues the same third-party data processing risk because it operates on a file previously uploaded off-host.

Content

Scanner excerpt · SKILL.md (reported line 141)May include surrounding context.

md
--data-binary "@$INPUT_PDF" | jq -r '.tool_result.data.file_id')

# Remove watermark
OUT_FILE_ID=$(curl -sS -X POST "$BASE/v1/tools/remove_watermark_pdf/execute" \
  -H "Content-Type: application/json" \
  -d "{\"file_id\":\"$IN_FILE_ID\",\"dpi\":144,\"timeout_sec\":180,\"output_mode\":\"file_id\"}" \
  | jq -r '.tool_result.data.file_id')

External Transmission

Medium
Category
Data Exfiltration
Confidence
60% confidence
Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 147)May include surrounding context.

md
| jq -r '.tool_result.data.file_id')

# Download
curl -sS -X POST "$BASE/v1/tools/download_file/execute?response_mode=raw" \
  -H "Content-Type: application/json" \
  -d "{\"file_id\":\"$OUT_FILE_ID\"}" \
  -o "$OUTPUT_FILE"

External Transmission

Medium
Category
Data Exfiltration
Confidence
93% confidence
Finding

The one-shot raw mode returns the processed PDF directly from the remote service, meaning the document is still processed externally after prior upload. This keeps the same privacy and compliance concerns while making the remote processing path slightly less visible because download is combined into a single step.

Content

Scanner excerpt · SKILL.md (reported line 166)May include surrounding context.

md
--data-binary "@$INPUT_PDF" | jq -r '.tool_result.data.file_id')

# Remove watermark + download in one call
curl -sS -X POST "$BASE/v1/tools/remove_watermark_pdf/execute" \
  -H "Content-Type: application/json" \
  -d "{\"file_id\":\"$IN_FILE_ID\",\"dpi\":144,\"timeout_sec\":180,\"output_mode\":\"raw\"}" \
  -o "$OUTPUT_FILE"

Static analysis

No suspicious patterns detected.