124-java-secure-coding

A reference for writing safer Java code. It covers checks on untrusted input, injection prevention, limited permissions, modern cryptography, safe error handling, secret storage, safer deserialization and output encoding.

In plain words
What is it for?
Reviewing or changing Java code to validate inputs, protect credentials, use safer cryptography and handle security-sensitive failures.
Why use it?
It helps reduce common security weaknesses such as SQL injection, exposed secrets, unsafe passwords and cross-site scripting. The guidance also keeps sensitive diagnostic details out of user-facing errors.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/jabrena/cursor-rules-examples/124-java-secure-coding
Any agent
npx skills add jabrena/cursor-rules-examples --skill 124-java-secure-coding
Clone the repo
git clone --depth 1 https://github.com/jabrena/cursor-rules-examples

Made for: Claude Code, Codex.

Per session 80 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 526 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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.

ModelPer sessionOnce invoked
Fable 5 $0.00080 $0.00526
Opus 5 $0.00040 $0.00263
Sonnet 5 $0.00016 $0.00105
Haiku 4.5 $0.00008 $0.00053

Measured yesterday against content hash 5e0f447c39c5, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

124-java-secure-coding 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 yesterday.

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.

.agents/skills/124-java-secure-coding/SKILL.md · 42 lines

What it actually says

Java Secure coding guidelines

Identify and apply Java secure coding practices to reduce vulnerabilities, protect sensitive data, and harden application behaviour against common attack vectors.

What is covered in this Skill?

  • Input validation: type, length, format, and range checks
  • SQL/OS/LDAP injection defence via PreparedStatement and parameterized APIs
  • Attack surface minimisation: least-privilege permissions, removal of unused features
  • Strong cryptography: BCrypt/Argon2 for passwords, AES-GCM for encryption, digital signatures; avoid deprecated ciphers (MD5, SHA-1, DES)
  • Secure exception handling: log diagnostic details internally, expose only generic messages to clients
  • Secrets management: load credentials from environment variables or secret managers — never hardcoded
  • Safe deserialization: strict allow-lists, prefer explicit DTOs over native Java serialization
  • Output encoding to prevent XSS in rendered content

Scope: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.

Constraints

Before applying any secure coding changes, ensure the project compiles. If compilation fails, stop immediately — do not proceed until resolved. After applying improvements, run full verification.

  • MANDATORY: Run ./mvnw compile or mvn compile before applying any changes
  • SAFETY: If compilation fails, stop immediately — do not proceed until the project is in a valid state
  • VERIFY: Run ./mvnw clean verify or mvn clean verify after applying improvements
  • BEFORE APPLYING: Read the reference for detailed good/bad examples, constraints, and safeguards for each secure coding pattern

When to use this skill

  • Review Java code for secure coding

Reference

For detailed guidance, examples, and constraints, see references/124-java-secure-coding.md.

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.

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.

  1. yesterday First seen · 42 lines · 80 tokens per session scan A 5e0f447c39c5

Subscribe to this mod's changes

124-java-secure-coding is a skill published in the GitHub repository jabrena/cursor-rules-examples (2 stars, last pushed 5d ago), licensed Apache-2.0. It adds 80 tokens to every session and 526 once invoked, about $0.0004 per session on Opus 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.

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