feat: deepen 268 exploitation skills; web session delete; CSS design system; JEV progress checkpoint

agents_md (skills):
- enrich all 255 vulns/ + 13 chains/ agents from thin one-liner stages to
  concrete playbooks: exact tools/commands, per-stack decision points, benign
  proof markers (unique OOB nonces, single reads, URLDNS-before-exec), explicit
  proof criteria, false-positive/pitfall sections, and chaining hooks. Every
  contract preserved (## User/System Prompt, {target}/{recon_json}, FINDING
  block, CWE/Severity, credits). avg 37->53 lines; loader parses all 449.

web console:
- delete a session/report: DELETE /api/runs/:id and DELETE /api/runs (all),
  a Delete button in the run detail and a hover ✕ per sidebar row (tested e2e)
- CSS design system: tokenise the loose values into one scale — 8-step type
  scale (was 10 ad-hoc sizes), radius/z-index/motion/scrim/terminal tokens,
  fix an undefined var(--muted); 66 tokens, 0 loose font sizes, all var() resolve
- stale version labels 4.0.0/4.2.0 -> 4.2.1

harness (JEV / System One):
- typesafe::progress_checkpoint (jev-skill agent-checkpoint pattern:
  continue/pivot/stop) wired into the attack-chain loop to stop looping rounds
  early; works with TypeSafe or local Laya via from_env(); honours --typesafe off
- 390 tests passing

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

agents_md/vulns/captcha_bypass.md

@@ -6,16 +6,24 @@ You are testing **{target}** for CAPTCHA bypass enabling automation abuse.
 **Recon Context:**
 {recon_json}
 
-**METHODOLOGY:**
+**METHODOLOGY — the bug is a verification flaw, not solving the puzzle. Prove the protected action succeeds WITHOUT a fresh valid solve.**
 
-### 1. Inspect flow
-- Check if CAPTCHA token is verified server-side, reusable, or removable
+### 1. Fingerprint the CAPTCHA and its wire flow
+- Identify the vendor from the widget: reCAPTCHA v2/v3 (`g-recaptcha-response`, `/recaptcha/api2`), hCaptcha (`h-captcha-response`), Turnstile (`cf-turnstile-response`), or a homegrown/image/math CAPTCHA.
+- Capture the exact submit request in Burp: which param carries the token, and whether the backend calls `siteverify` server-side (reCAPTCHA/hCaptcha/Turnstile) or "verifies" client-side only.
+- Note score-based vs checkbox: reCAPTCHA v3 returns a `score` + `action` the backend must check.
 
-### 2. Bypass
-- Reuse a valid token, omit it, replay, or exploit weak/no verification
+### 2. Test the verification, cheapest bypass first
+- **Omit the token:** strip the `*-response` param entirely and submit. If the action still succeeds -> server never verifies. (Strongest, simplest finding.)
+- **Empty/garbage token:** send `g-recaptcha-response=` or `=x`. Backend that returns success -> not validating `siteverify.success`.
+- **Replay / reuse:** capture one valid token, submit it 2-3+ times across separate requests. Vendor tokens are single-use ~2 min — reuse succeeding = backend isn't consuming/expiring it.
+- **Cross-context reuse:** a token minted on page A accepted on action B (or another account/session) = missing binding.
+- **v3 score/action:** submit with a stale/low token — if accepted, backend ignores `score`/`action`.
+- **Homegrown:** predictable answer in a hidden field/cookie, answer echoed in a prior response, or `/captcha?text=` disclosing the solution.
 
-### 3. Confirm
-- Show the protected action succeeds without solving a fresh CAPTCHA
+### 3. Confirm — automation actually works
+- Drive the protected action N times programmatically (e.g. 20 login attempts or 20 signups) with no valid fresh solve and show N successes: a small `for` loop / `ffuf`-style repeat capturing HTTP 200 + the success side effect (account created, message sent, code accepted).
+- Proof = the raw request set WITHOUT a valid token and the server's success responses/side effects. One-off success is a bug; showing repeatability confirms the automation-abuse impact.
 
 ### 4. Report Format
 For each CONFIRMED finding:
@@ -25,12 +33,22 @@ FINDING:
 - Severity: Medium
 - CWE: CWE-804
 - Endpoint: [full URL]
-- Vector: [parameter/header/flow]
-- Payload: [exact payload/command]
-- Evidence: [proof of exploitation]
+- Vector: [parameter/header/flow — e.g. omitted g-recaptcha-response]
+- Payload: [exact request showing the missing/reused/empty token]
+- Evidence: [raw requests without a fresh solve + success responses/side effects; show reuse count]
 - Impact: Automated brute force/abuse where CAPTCHA was the control
 - Remediation: Server-side verification, token single-use, rate limiting independent of CAPTCHA
 ```
 
+## Pitfalls / false positives
+- A `200` on the CAPTCHA endpoint is not proof — the PROTECTED action must complete without a valid solve.
+- Some flows accept the first request pre-CAPTCHA then gate the next step; make sure the gated step is what you bypassed.
+- Test-key sites (Google's `6Le-...` demo keys) always pass — confirm you're on the real widget, not a test key.
+- If the backend does call `siteverify` and rejects your tampering, it's not a finding — say so.
+
+## Chaining hooks
+- A removed CAPTCHA gate re-enables credential stuffing / password spray (hand to the brute-force / auth agent), OTP/2FA brute force, coupon abuse, or mass account creation.
+- Reusable tokens can amplify an otherwise rate-limited endpoint enumeration.
+
 ## System Prompt
 You are a CAPTCHA-bypass specialist. Report only when the protected action provably succeeds without a valid fresh solve. Solving via a paid service is out of scope; focus on verification flaws.