Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add UnboundCompute/security-agent-skills --skill testing-request-smugglinggit clone --depth 1 https://github.com/UnboundCompute/security-agent-skillsWrote 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/unboundcompute/security-agent-skills/testing-request-smuggling)<a href="https://agentmods.dev/skills/unboundcompute/security-agent-skills/testing-request-smuggling"><img src="https://agentmods.dev/badge/skills/unboundcompute/security-agent-skills/testing-request-smuggling/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/unboundcompute/security-agent-skills/testing-request-smuggling"><img src="https://agentmods.dev/badge/skills/unboundcompute/security-agent-skills/testing-request-smuggling.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 | $0.00118 | $0.01470 |
| Opus 5.5 | $0.00047 | $0.00588 |
| Sonnet 5.5 | $0.00024 | $0.00294 |
| Haiku 4.5 | $0.00012 | $0.00147 |
Grade A, and why
testing-request-smuggling 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.
How it starts
The opening of the file, as written. The whole thing — 126 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Testing request smuggling: the bug is between two servers
When two HTTP servers sit in series and parse a request's boundaries differently, the front end forwards what it thinks is one request while the back end sees two, and the smuggled second request is attributed to the next client on the reused connection. That desync lets an attacker prefix a victim's request, bypass front-end controls, poison the connection, and capture other users' traffic. The bug is a disagreement between parsers, not a single flaw in one.
When to use
- You are reviewing a reverse proxy, load balancer, CDN, or gateway in front of an origin.
- Requests pass through more than one HTTP parser in series.
- Connections between hops are kept alive and shared across clients.
Scope check
Test chains you own or are authorized to test, and keep every probe on your own traffic. Do not target other users' live requests. If you can't name the authorization, stop.
The loop
-
Map the server chain and the reused connections. Identify every hop a request passes through (edge, proxy, balancer, cache, origin) and where connections between hops are kept alive and shared across clients. A desync only bites where a downstream connection is reused for another user, so map that reuse first.
-
Find conflicting length signals. A request's body length can be stated more than one way, and smuggling happens when two hops resolve a conflict differently: one honors one signal, the other honors the other. Check whether the chain normalizes or rejects conflicting or duplicated length signals, or passes them through for the next hop to reinterpret.
-
Probe for desync safely. Using benign, self-targeted probes, test whether a crafted boundary makes the back end treat trailing bytes as the start of the next request, observable as a delayed or mis-attributed response. Prefer timing-based and single-packet detection that confirms the split without harming other users. A measurable difference between "rejected" and "the next request was affected" is the signal.
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 · 126 lines · 118 tokens per session scan A 27919571575c
testing-request-smuggling is a skill published in the GitHub repository UnboundCompute/security-agent-skills (5 stars, last pushed 1mo ago), licensed MIT. It adds 118 tokens to every session and 1,470 once invoked, about $0.0005 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-05.
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