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Tom's Hardware challenges Mythos zero-day claims

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A technical review found Anthropic's marketing relied on 198 manual reviews to support claims of thousands of severe vulnerabilities.

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Key takeaway

Only 198 manual reviews support Anthropic's claim of thousands of zero-day discoveries.

Tom's Hardware published a critical review of Anthropic's Mythos claims on 9 April, noting that the "thousands of zero-days" assertion rested on only 198 manual reviews ¹. Many of the flagged vulnerabilities were in outdated software no longer in active use. The gap between Anthropic's marketing language and the verified sample is wide enough to warrant caution.

The Bessent-Powell emergency meeting at Treasury headquarters proceeded regardless of this scrutiny. Challenger data confirmed AI-attributed cuts crossed 107,094 the same month , suggesting federal regulators assessed the systemic risk of AI broadly, beyond Mythos's specific claims. Whether Mythos found hundreds or thousands of exploitable flaws, the CyberGym benchmark score of 83.1% versus 66.6% for its predecessor represents a measurable capability jump that the twelve Glasswing partners will deploy in production environments.

Deep Analysis

In plain English

When Anthropic announced that Claude Mythos had found 'thousands' of serious security flaws in software, it was a dramatic claim. Tom's Hardware, a technology publication, looked at how Anthropic had actually counted those flaws. The answer was: 198 human reviewers manually checked the model's outputs. Many of the flaws it identified were in old software that organisations had already stopped using. The gap between 'thousands of vulnerabilities' and 198 verified reviews is significant. The US Treasury and Federal Reserve held their emergency meeting with bank CEOs regardless of this critique, which suggests the regulators assessed the risk from the model's overall capability trajectory, not just the specific zero-day count.

Source Landscape

This story draws on neutral-leaning sources

Primary parallel: The 2016 controversy over DeepMind's AlphaGo claims, in which Google's marketing described the system as defeating the world champion 'under official match conditions' when several conditions differed from tournament rules. Independent verification eventually confirmed the underlying capability while correcting specific claim framing. The Mythos methodology question follows the same pattern: contested marketing language around a genuine capability advance.

Counter-parallel: IBM's 1997 Deep Blue versus Kasparov match produced verified, independently adjudicated results that settled the capability claim definitively. Cybersecurity benchmarks lack equivalent independent adjudication, making the gap between Anthropic's 198-review sample and its 'thousands' headline durable in ways that chess results were not.

Consensus view: Trail of Bits co-founder Dan Guido and Veracode's Chris Wysopal assess the 198-review gap as a credibility problem for Anthropic's marketing rather than a refutation of the underlying capability: the CyberGym benchmark improvement from 66.6% to 83.1% is independently verifiable, and that gap is operationally significant regardless of zero-day count methodology.

Counter-view: Recorded Future's intelligence analysts note that threat actors routinely inflate capability claims to generate deterrence value, and that AI vendors have structural incentives to do the same. Overstated AI security capabilities may cause organisations to misallocate defensive resources toward theoretical AI attack vectors while under-investing in conventional vulnerability management.

Key tension: Whether the verified CyberGym benchmark gain represents a genuine operational security threat or a marketing projection requiring independent validation before driving regulatory and corporate resource allocation.

Sources:Tom's Hardware

Mentions:Google →US Treasury →CyberGym →Federal Reserve →Prima →Anthropic →Claude Mythos Preview →

First Reported In

Update #5 · The model they won't release

Tom's Hardware· 10 Apr 2026

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Causes and effects

This Event

Tom's Hardware challenges Mythos zero-day claims

Independent scrutiny of Mythos's capability claims introduces uncertainty about the model's actual security impact, even as regulators acted on the headline numbers.

Led to

AISI confirms Mythos 20-hour attack chain

AISI partly vindicates Tom's Hardware's critique of single-task superiority claims while confirming a distinct attack-chaining capability the Hardware review did not assess.

Occurred 15 Apr 2026

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Different Perspectives

Barclays

Barclays economist Pooja Sriram flagged a 28,000-a-month bleed in finance and information roles the same week Microsoft disputed that AI drove its own 4,800 cuts. The bank treats Challenger's AI-attribution share as a lagging indicator against faster erosion visible in raw labour-market data.

European Commission

Brussels deferred the Digital Omnibus's Annex III employment-compliance deadline from 2 August 2026 to December 2027, even as California advanced three binding AI-hiring bills the same week. The 17-month delay leaves EU workers without the algorithmic-hiring safeguards the regulation already promises.

OpenAI

OpenAI proposed a 5% US government equity stake worth $42.6bn, structured as a public wealth fund modelled on the Alaska Permanent Fund, with Sam Altman pitching it directly to Trump, Bessent and Lutnick. The offer pre-empts Sanders' rival one-time 50% AI-stock tax, which has not yet reached committee.

India's IT and outsourcing sector

BAT's transfer of 3,500 roles to Accenture on 29 June fits a delivery model Indian IT firms increasingly run: consultancies win Western contracts, then execute through offshore centres. The sector expects more Fit2Win-style transfers, not straight redundancies, as employers absorb AI without cutting outsourced headcount.

European Trade Union Confederation

ETUC says the Council's shift from 'ensure' to 'support' in the AI-literacy duty, confirmed in the Digital Omnibus's final adoption on 29 June, is a collapse of the legal threshold, not a drafting tidy-up. It expects EU workers to face AI-driven hiring and monitoring decisions with a statutory right to explanation that exists in name only.

British American Tobacco's Fit2Win workforce

BAT is cutting 9,000 roles under Fit2Win, transferring 3,500 to Accenture rather than making them redundant, to reach roughly £500m in AI-driven savings by 2027. For affected staff, that distinction decides whether they keep a job at all, just not at BAT.