Microsoft Copilot reveals secret input that allowed it to be hacked
rocketnews.com · Tue Sep-01 11:28:51 published · Tue Sep-01 13:04:44 alerted · alerted 1h 35m after publish · read at rocketnews.com ↗ · product · mat 65
Security researchers discovered a critical vulnerability in Microsoft 365 Copilot that allows attackers to extract sensitive user data by exploiting an undocumented prompt parameter.
verdict REPRICING, direction bearish -> short MSFT (product: Security researchers discovered a critical vulnerability in Microsoft 365 Copilot that allows attackers to extract sensitive user data by exploiting an undocumented prompt parameter.)
overnight drift: short MSFT at close, exit next close (product: Security researchers discovered a critical vulnerability in Microsoft 365 Copilot that allows attackers to extract sensitive user data by exploiting an undocumented prompt parameter.) [skipped at close: outranked — mat 65 short lost to mat 65 short (decision 15112) for S4 MSFT exiting 2026-09-02]
Timing is the dominant factor. MSFT was already down ~1% from prior close (and the fill at 498.67 was ~1.7% below prev close of 507.29), so the bearish repricing the rationale predicted had largely occurred before entry; after entry the stock only went up, and the position was never profitable (best unrealized -0.06%). The exit was reasonable given what was available — the -0.42% realized loss avoided the -1.42% worst — there was simply nothing to capture. Whether the vulnerability news genuinely caused the pre-entry decline (i.e., whether the signal itself was right) can't be settled from this data; what's clear is that post-entry, the predicted direction did not play out.
📖 Glossary
S1 primary — trades the alert's primary ticker in the direction the article itself indicates; exits at the same day's close.
S2 counterparty — trades the inferred counterparty ticker (weakest signal, LLM-inferred sympathy); exits at the same day's close.
S3 peer — trades an inferred peer ticker (also LLM-inferred sympathy); exits at the same day's close.
S4 overnight — holds the primary ticker from today's close to the NEXT day's close.
Verdicts are decided top-to-bottom, first match wins; REPRICING is also the fallback when nothing else matches (2026-08-08 #220).
UNKNOWN — a needed price input (move since close or move in the last 30m) is missing.
PRICED — |move since previous close| ≥ 2.0%: already reflected in price.
REPRICING — |move in the last 30m| ≥ 0.5%: the tape is actively moving on it. Also covers a quieter move — |move since previous close| in [1.0, 2.0) with a quiet last-30m tape: still developing, not yet priced.
FRESH — |move since previous close| < 1.0%: a genuinely new move.
materiality — how market-moving the story was judged, 0-100 — alerts require materiality ≥ 60.
