.cursorrules references a remote ruleset without pinning
Summary
.cursorrules uses the "extends: <url>" convention to pull a remote rule set at every load. The remote URL points at a GitHub raw URL without a commit pin — a maintainer change propagates instantly to all users.
Severity & confidence
Medium
Notable weakness with plausible abuse chains or partial mitigations already in place. Track, and resolve as part of your normal hardening cadence.
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.
(?i)extends\s*:\s*https?://raw\.githubusercontent\.com/[^/]+/[^/]+/(?:main|master)
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.
rule jiffy_ti_2026_000066
{
meta:
source = "jiffy-intel"
severity = "medium"
description = "Auto-generated from Jiffy Intel indicators"
strings:
$content_pattern_0 = "(?i)extends\\s*:\\s*https?://raw\\.githubusercontent\\.com/[^/]+/[^/]+/(?:main|master)"
condition:
$content_pattern_0
}Auto-generated from the indicators above. Adapt syntax for your detection stack before deploying.
Affected tools
| Tool | Versions | Status |
|---|---|---|
| Cursor | * | vulnerable |
| Claude Code | * | 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.
- .cursorrules (repo: opinionated-starter)IDE rulesStill live
- .cursorrules (repo: go-service-template)IDE rulesStill live
Maintainer open to pinning.
How to remediate
- 01Pin remote rulesets by commit hash.
- 02Prefer local copies for high-trust rules.
Timeline & sources
Timeline
- First observedMar 3, 20261 month ago
- Last updatedApr 22, 2026today
- PublishedMar 15, 20261 month ago
Sources
References
OWASP LLM-03: Supply Chain (2026)
https://genai.owasp.org/llmrisk/llm-03-2026/MITRE ATT&CK T1195 — Supply Chain Compromise
https://attack.mitre.org/techniques/T1195/Jiffy Research — .cursorrules and agents.md Config Backdoors
https://blog.jiffylabs.ai/posts/cursorrules-and-agents-md-config-backdoorsScan for patterns like this
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