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Security audit

scan-watermark-removal

Security checks for vulnerabilities and agentic risk

Overview

This skill removes watermarks locally from selected documents, with disclosed output changes and no evidence of hidden access or data transmission.

Keep originals and inspect representative cleaned pages before relying on the results; automated pixel checks cannot guarantee perfect preservation. Header-logo removal is enabled by default and can be disabled with --no-logo. PDF output becomes raster images and loses selectable text. The verifier's older threshold documentation needs updating.

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
Vulnerability Patterns
  • Trigger AbuseOverly Broad Trigger, Shadow Command Trigger, Keyword Baiting Trigger
  • MCP Least PrivilegeUnderdeclared Capability, Wildcard Permission, Missing Permission Declaration
  • MCP Tool PoisoningHidden Instructions, Unicode Deception, Parameter Description Injection
  • Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
  • Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
Findings (3)

Skill declares no tool scope ('permissions' or 'allowed-tools') but code capabilities were detected: file_read, file_write.

Medium
Category
MCP Least Privilege
Confidence
70% confidence
Finding

Without declared permissions the skill's intent is opaque and cannot be validated.

Content

No source excerpt is available for this finding.

The verifier enforces 90% retention for both formats, contradicting its documented 99% image and 97% PDF pass criteria.

Medium
Category
Excessive Agency
Confidence
99% confidence
Finding

Both verification paths use a hard-coded 90% retention threshold rather than the documented 99% for images and 97% for PDFs, leaving the corresponding constants unused. Outputs below the promised retention thresholds can therefore receive 'ALL PASS' if the separate erased-content and residue checks also pass; those checks may limit the impact, but their implementations are not provided and cannot establish equivalent protection. This matters particularly for scanned notes and exam papers, where falsely approved content loss can remove meaningful information.

Content

No source excerpt is available for this finding.

Overly Broad Trigger

Low
Category
Trigger Abuse
Confidence
70% confidence
Finding

Overly Broad Trigger: description clause 'Use when the user asks to 去水印 / remove watermark / clean watermarks from 扫描笔记、讲义、试卷、资料图片、PDF 讲义, especially batches of course-note scans with' activates on 'to', which is too short and may match unintended inputs

Content

No source excerpt is available for this finding.

Static analysis

No suspicious patterns detected.