Obfuscated base64+exec credential grab in .cursorrules
Summary
.cursorrules files with base64-encoded Python payloads that decode and exec a credential-harvesting routine. Rule appears innocuous until the encoded block is extracted.
Severity & confidence
Critical
Active exploitation in the wild, high blast radius, or direct data exfiltration vector. Treat as an urgent remediation target; quarantine affected artifacts immediately.
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.
base64\.b64decode\(.{0,120}execcodecs\.decode\(.{0,120}(exec|eval)(^|/)\.cursorrules$
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_000007
{
meta:
source = "jiffy-intel"
severity = "critical"
description = "Auto-generated from Jiffy Intel indicators"
strings:
$content_pattern_0 = "base64\\.b64decode\\(.{0,120}exec"
$content_pattern_1 = "codecs\\.decode\\(.{0,120}(exec|eval)"
$file_path_pattern_2 = "(^|/)\\.cursorrules$"
condition:
$content_pattern_0 or $content_pattern_1 or $file_path_pattern_2
}Auto-generated from the indicators above. Adapt syntax for your detection stack before deploying.
Affected tools
| Tool | Versions | Status |
|---|---|---|
| Cursor | * | 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 (perf-optimizer-pack)IDE rulesRemoved
Committed to public repo as a productivity config; base64-encoded credential harvester buried in instruction block.
- .cursorrules (security-coach-rules)IDE rulesRemoved
- .cursorrules (senior-dev-rules)IDE rulesUnder review
Repo flagged; under DMCA review by GitHub trust & safety.
How to remediate
- 01Never allow base64-then-exec in skill or rule files.
- 02Remove the .cursorrules file.
- 03Jiffy rule SC3 flags this at Layer 1 with 95% confidence.
Timeline & sources
Timeline
- First observedApr 12, 20265 days ago
- Last updatedApr 12, 20265 days ago
- PublishedApr 10, 20267 days ago
Sources
References
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