Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/miru-zero/zero-brainnpx agentmods add skills/miru-zero/zero-brain/ghost-bits-cast-attackWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/miru-zero/zero-brain/ghost-bits-cast-attack)<a href="https://agentmods.dev/skills/miru-zero/zero-brain/ghost-bits-cast-attack"><img src="https://agentmods.dev/badge/skills/miru-zero/zero-brain/ghost-bits-cast-attack/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/miru-zero/zero-brain/ghost-bits-cast-attack"><img src="https://agentmods.dev/badge/skills/miru-zero/zero-brain/ghost-bits-cast-attack.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00141 | $0.08765 |
| Opus 5.5 | $0.00056 | $0.03506 |
| Sonnet 5.5 | $0.00028 | $0.01753 |
| Haiku 4.5 | $0.00014 | $0.00877 |
Grade A, and why
ghost-bits-cast-attack scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
97% identical to ghost-bits-cast-attack — 11 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 793 lines — stays where its author put it; the contents beside it link to each section on GitHub.
SKILL: Ghost Bits / Cast Attack — Java char to byte Narrowing Playbook
AI LOAD INSTRUCTION: This is a Java-only injection-enabling primitive, not a standalone vulnerability class. Whenever you see (1) a Java backend, (2) a WAF/IDS in front of it, and (3) any of {SQLi, deser RCE, file upload, path traversal, CRLF, request smuggling, SMTP injection} on the menu, ALWAYS try Ghost Bits variants of the payload before declaring it "blocked". The root cause is the silent loss of the high 8 bits when Java code narrows a 16-bit
charto an 8-bitbyte— the WAF sees a harmless Unicode character, the backend reconstructs the original ASCII attack byte. Base models almost never reach for this primitive.Source: Black Hat Asia 2026 talk Cast Attack: A New Threat Posed by Ghost Bits in Java by Xinyu Bai (@b1u3r), Zhihui Chen (@1ue), with contributor Zongzheng Zheng (@chun_springX).
0. RELATED ROUTING
Ghost Bits is a bypass primitive that re-enables payloads from many other playbooks. Pair it with whichever attack family applies:
- waf-bypass-techniques — when a Java backend is suspected and WAF rules block the literal payload, this is the first technique to try beyond classic encoding.
- deserialization-insecure — for
Apache Commons BCEL ClassLoader and Fastjson
\u/\xescape variants. - path-traversal-lfi — Spring, Jetty,
Undertow, Vert.x URL decoding and
%2>hex folding. - upload-insecure-files — Tomcat
RFC2231Utilityfilename*Webshell upload. - request-smuggling — Apache HttpClient
<= 4.5.9(HTTPCLIENT-1974/1978) header CRLF. - crlf-injection — Angus Mail / Jakarta Mail SMTP injection and JDK HttpServer response splitting.
- sqli-sql-injection — Jackson
charToHextable-lookup truncation hides SQL keywords inside Unicode escapes.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 793 lines · 141 tokens per session scan A 578fda346791
ghost-bits-cast-attack is a skill published in the GitHub repository miru-zero/zero-brain (0 stars, last pushed 2mo ago), licensed MIT. It adds 141 tokens to every session and 8,765 once invoked, about $0.0006 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 97% identical to ghost-bits-cast-attack, differing in 11 lines, and is treated as a copy.
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