Slack AI could be tricked into leaking private-channel data via indirect prompt injection

data-exfiltration security-fail

Attribution Anonymous

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Incident Summary

PromptArmor disclosed in August 2024 that Slack AI could be manipulated through indirect prompt injection: an attacker posting in any public channel could plant instructions that, when a victim later queried Slack AI, caused it to render a markdown link exfiltrating private-channel content (such as secrets or API keys) to the attacker's server via the URL — without the attacker ever accessing the private data directly. A later update that pulled files and DMs into answers widened the attack surface. Slack deployed a patch.

Case Analysis

Verified Facts

PromptArmor disclosed indirect prompt injection in Slack AI in Aug 2024
An attacker needed only to post in a public channel
Private-channel content could be exfiltrated via a rendered markdown link
Slack deployed a patch

Not Publicly Confirmed

Whether the technique was exploited in the wild

Operational Lessons

→Treat all retrieved content as untrusted input to the model
→Block model-rendered links that can carry data to arbitrary domains

Primary Source

Slack AI can leak private data via prompt injection (The Register)theregister.com ↗

Discussion

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