What is security-input-validation-and-dangerous-sinks?

A security guide for handling untrusted input before it reaches risky operations such as SQL queries, HTML output, files, shell commands, or redirects.

Use it to choose the right protection for each destination, such as parameterized SQL, HTML encoding, path restrictions, and redirect allowlists.

It helps prevent attacks caused by sending user-controlled data into operations that can execute code, alter data, read files, or redirect users.

security-input-validation-and-dangerous-sinks

Install

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.

Any agent

npx skills add andrewsrigom/agent-skills --skill security-input-validation-and-dangerous-sinks

Clone the repo

git clone --depth 1 https://github.com/andrewsrigom/agent-skills

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/andrewsrigom/agent-skills/security-input-validation-and-dangerous-sinks/github.svg)](https://agentmods.dev/skills/andrewsrigom/agent-skills/security-input-validation-and-dangerous-sinks)

Your own site

<a href="https://agentmods.dev/skills/andrewsrigom/agent-skills/security-input-validation-and-dangerous-sinks"><img src="https://agentmods.dev/badge/skills/andrewsrigom/agent-skills/security-input-validation-and-dangerous-sinks/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/andrewsrigom/agent-skills/security-input-validation-and-dangerous-sinks"><img src="https://agentmods.dev/badge/skills/andrewsrigom/agent-skills/security-input-validation-and-dangerous-sinks.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 474 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00051	$0.00474
Opus 5.5	$0.00020	$0.00190
Sonnet 5.5	$0.00010	$0.00095
Haiku 4.5	$0.00005	$0.00047

Measured 2mo ago against content hash 24f938d348ca, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

security-input-validation-and-dangerous-sinks 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 2mo 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.

security/security-input-validation-and-dangerous-sinks/SKILL.md · 72 lines

How it starts

The opening of the file, as written. The whole thing — 72 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Security Input Validation And Dangerous Sinks

Use this skill when the risk comes from attacker-controlled input flowing into a dangerous sink.

Scope

input validation
normalization
parameterized database access
HTML and output-context encoding
shell, path, redirect, and URL sink safety

Default path

Name the untrusted input source.
Name the dangerous sink it can reach.
Validate and normalize input once near entry.
Use sink-specific protection:
- parameterized queries for SQL
- context-appropriate escaping or encoding for HTML
- path allowlists or fixed roots for filesystem access
- no shell interpolation for command execution
- redirect allowlists for outbound navigation
Keep raw attacker input away from privileged sinks when possible.

When to deviate

Use richer schema validation only when the domain actually needs structured coercion or refinement.
Allow limited rich text only with a deliberate sanitization and rendering boundary.
Use raw input logs sparingly and only with redaction when sensitive data may be present.

Guardrails

Validation is not generic string cleaning.
Protection must match the sink, not just the input type.
Normalize once; avoid multiple inconsistent parsing paths.
Prefer avoiding dangerous sinks entirely when the feature design allows it.

Avoid

“sanitize everything” with no sink model
string-concatenated SQL
trusting file paths or redirect targets from raw input
assuming one HTML sanitizer solves shell, SQL, and URL problems too

Verification checklist

source input is named
dangerous sink is named
validation and normalization happen once
sink-specific protection is used
raw attacker input is not flowing unchecked into privileged operations

Output Shape

When answering with this skill, prefer:

untrusted source
dangerous sink
required validation
required sink-specific protection
main exploit path if left unchanged

References

Validation and sink defaults

Read the full file on GitHub · 72 lines

Files

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.

references/validation-and-sink-defaults.md 404 B

Changes

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.

2mo ago First seen · 72 lines · 51 tokens per session scan A 24f938d348ca

Subscribe to this mod's changes

security-input-validation-and-dangerous-sinks is a skill published in the GitHub repository andrewsrigom/agent-skills (2 stars, last pushed 7mo ago), licensed MIT. It adds 51 tokens to every session and 474 once invoked, about $0.0002 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 2026-08-31.