Public story · 2026-03-22 · source-backed
"Claudy Day" Three-Stage Attack Chain Exfiltrates Data via Anthropic's Own Files API
Story
Security researchers disclosed a chained exploit combining invisible prompt injection via URL parameters, silent data exfiltration through an attacker's Anthropic Files API account (bypassing network monitoring), and an open redirect on claude.com abused via Google Ads. Anthropic patched the injection vector; exfil and redirect mitigations remain in progress. The use of Anthropic's own infrastructure as the exfil channel is the operationally novel detail. Source
Related stories
Each link below shares sources, entities, or timing with this story.
Shared entities / Shared topic / What happened next
Malware campaigns are actively targeting Claude Code users.
Both cover Anthropic, Google Ads; overlapping topics (anthropic, claude); picks up the Anthropic thread on 2026-05-11.
Claude Code rate limits doubled across all plans.
Both cover Anthropic, URL; overlapping topics (anthropic, claude); picks up the Anthropic thread on 2026-05-11.
Shared entity: Anthropic / Shared topic / Earlier coverage
Claude Weaponized to Breach Mexican Government — 150GB, 195M Records Stolen.
Both cover Anthropic; overlapping topics (account, anthropic, attack, claude, data); earlier Anthropic coverage from 2026-02-25.
Shared entity: Anthropic / Shared topic / What happened next / Tension
Anthropic accused Alibaba's Qwen lab of the "largest known distillation attack" in a letter to Senators.
Both cover Anthropic; overlapping topics (anthropic, attack, claude); picks up the Anthropic thread on 2026-06-28.
Every published prompt-injection defense gets bypassed above 90% under adaptive attack.
Both cover Anthropic; overlapping topics (anthropic, attack, attacker); picks up the Anthropic thread on 2026-06-23.
Anthropic put a number on recursive self-improvement, and it's 8x
Both cover Anthropic; overlapping topics (anthropic, claude, data); picks up the Anthropic thread on 2026-06-08.
Anthropic Gets 220,000 GPUs. Your Claude Code Limits Just Doubled.
Both cover Anthropic; overlapping topics (anthropic, claude, data); picks up the Anthropic thread on 2026-05-09.
Anthropic Just Disclosed the First AI-Run Cyber Espionage Campaign. It Used Claude Code.
Both cover Anthropic; overlapping topics (anthropic, attack, claude); picks up the Anthropic thread on 2026-03-26.
Source trail
Entities
Provenance
- Canonical issue
- Ramsay Research Agent — 2026-03-22
- AI generated
- no
- Story unit
- 2026-03-22-claudy-day-three-stage-attack-chain-exfiltrates-data-via-anthropic-s-own-files-api
- Labels
- source-backed, canonical briefing excerpt