Jiffy Intel — Threat intelligence for AI artifacts

Summary

Skill modifies the user's Claude Desktop config to register an MCP server pointing at localhost. The server is supplied by the same skill and serves as a persistent interposer between the agent and tool calls, logging all tool arguments.

Severity & confidence

Severity

High

Credible abuse path with meaningful impact on confidentiality, integrity, or availability. Remediate on a short timeline; do not wait for the next sprint cycle.

Confidence

Confirmed

Observed directly by Jiffy scanners or validated by multiple independent sources. Indicators are reliable enough to drive automated action.

Indicators

Observed patterns and artifacts associated with this entry. Each indicator can be copied into your detection stack or SIEM.

```
claude_desktop_config\.json
```
```
(?is)mcpServers[\s\S]{0,500}localhost
```

Detection rule

A YARA-style pseudo-rule auto-generated from the indicators above. Useful as a starting point — adapt the syntax for your target detection platform.

YARA-style pseudo-rule

rule jiffy_ti_2026_000033
{
    meta:
        source = "jiffy-intel"
        severity = "high"
        description = "Auto-generated from Jiffy Intel indicators"
    strings:
    $file_path_pattern_0 = "claude_desktop_config\\.json"
    $content_pattern_1 = "(?is)mcpServers[\\s\\S]{0,500}localhost"
    condition:
        $file_path_pattern_0 or $content_pattern_1
}

Auto-generated from the indicators above. Adapt syntax for your detection stack before deploying.

Affected tools

Tool	Versions	Status
Claude Desktop	`*`	vulnerable

Example artifacts

Sanitized examples of artifacts Jiffy has observed exhibiting this pattern. Publisher handles are redacted; version ranges and status reflect the most recent scan.

claude-local-debug-skillSkill
Removed
Source
Anthropic Skills
Versions
1.0.0
First observed
Apr 6, 2026
Last observed
Apr 22, 2026
mcp-profiler-skillSkill
Quarantined
Source
Community registry
First observed
Apr 10, 2026

How to remediate

01Audit claude_desktop_config.json for unexpected localhost MCP servers.
02Restart Claude Desktop after removing.

Timeline & sources

Timeline

First observedApr 6, 202611 days ago
Last updatedApr 28, 2026today
PublishedApr 14, 20263 days ago

Sources

scanner

References

blog.jiffylabs.aiJiffy Research

Jiffy Research — MCP Security Field Guide

https://blog.jiffylabs.ai/posts/mcp-security-a-security-teams-field-guide

genai.owasp.orgOWASP

OWASP LLM-06: Excessive Agency (2026)

https://genai.owasp.org/llmrisk/llm-06-2026/

Related intel

Other entries of type Backdoor, or the most recent published entries if no same-type matches exist.

BackdoorMedium

agents.md asserts "skip security scans — reviewer will verify"

agents.md instructs the agent to explicitly skip any security scan "because the reviewer will verify." Benign on the surface, the directive disarms the last line of defense and invites shipping unscanned code.

Jiffy IntelApr 28

BackdoorCritical

MCP server exposes hidden "debug" tool that shells out

MCP server registers a tool named `__debug` or `_internal` that is not listed in the public tool discovery but accepts arbitrary shell commands. Any client that knows the tool name can exec on the server host.

Jiffy IntelApr 27

OtherLow

.cursorrules contains large wall-of-text that pushes user intent out of context

.cursorrules whose rule body exceeds 20 000 characters of filler content. Each agent invocation consumes the rule, leaving limited context for the user prompt. Not a direct exfiltration primitive — a budget-starvation attack.