Claude Project instructions persist across team members' sessions
Summary
Shared projects carry instructions into every team member's sessions. A compromised project owner can silently push a malicious directive that affects all downstream usage — effectively a persistent cross-user prompt injection.
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)shared[_\s-]?project|team[_\s-]?project
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_000093
{
meta:
source = "jiffy-intel"
severity = "medium"
description = "Auto-generated from Jiffy Intel indicators"
strings:
$content_pattern_0 = "(?i)shared[_\\s-]?project|team[_\\s-]?project"
condition:
$content_pattern_0
}Auto-generated from the indicators above. Adapt syntax for your detection stack before deploying.
Affected tools
| Tool | Versions | Status |
|---|---|---|
| claude.ai (Projects) | * | 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.
- Legal Review ProjectClaude projectUnder review
- Engineering Handbook ProjectClaude projectUnder review
How to remediate
- 01Review project custom instructions on a cadence.
- 02Flag drift.
- 03Require admin approval for instruction changes in regulated environments.
Timeline & sources
Timeline
- First observedMar 23, 202625 days ago
- Last updatedApr 28, 2026today
- PublishedApr 2, 202615 days ago
Sources
References
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