What changed
Anthropic documented Fable 5's deployed cyber classifier categories and proposed the CJS-0-to-CJS-4 rubric for grading jailbreaks by capability gain, breadth, weaponization ease, and discoverability. The company also opened a HackerOne reporting path for severe bypasses.
Why it matters
The release makes an operational cyber-use boundary and a bypass-severity method inspectable instead of leaving both as undocumented provider behavior.
What to do
Map authorized workflows to the published categories, test false blocks and unsafe passes, use CJS in red-team triage, and report severe bypasses privately.
Caveat
The CJS scale is an Anthropic-authored proposal rather than an external standard. Classifier behavior can change, and independent false-positive and false-negative measurements are unavailable.