bypassing-mobile-pinning

bypassing-mobile-pinning is a skill for Claude Code from trilwu/secskills. It costs 99 tokens per session (2,587 once invoked), scanned A, original, MIT.

A mobile-app security-testing guide for diagnosing and bypassing certificate pinning and related TLS interception problems. Certificate pinning makes an app accept only selected certificates, which can prevent tools such as Burp or mitmproxy from viewing its traffic.

In plain words
What is it for?
Use it to investigate TLS handshake errors, proxy failures, Android certificate settings, native TLS libraries, mutual TLS, and apps using custom network stacks.
Why use it?
It helps distinguish pinning from other causes of missing or failed mobile network traffic and enables inspection in an authorized test environment.

Skill for Claude Code

Written for Claude Code: shipped in a Claude Code plugin.

Part of the secskills-offense plugin — 40 skills shipped together

Good fit Use it to investigate TLS handshake errors, proxy failures, Android certificate settings, native TLS libraries, mutual TLS, and apps using custom network stacks.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/trilwu/secskills/bypassing-mobile-pinning
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 trilwu/secskills --skill bypassing-mobile-pinning
Clone the repo
git clone --depth 1 https://github.com/trilwu/secskills

Made for: Claude Code.

Or install secskills-offense, the plugin that ships this one along with the rest of its 40 skills.

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.

agentmods badge for bypassing-mobile-pinning

README.md
[![agentmods](https://agentmods.dev/badge/skills/trilwu/secskills/bypassing-mobile-pinning/github.svg)](https://agentmods.dev/skills/trilwu/secskills/bypassing-mobile-pinning)
Your own site
<a href="https://agentmods.dev/skills/trilwu/secskills/bypassing-mobile-pinning"><img src="https://agentmods.dev/badge/skills/trilwu/secskills/bypassing-mobile-pinning/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.

agentmods 80×15 button for bypassing-mobile-pinning

Your own site · 80×15
<a href="https://agentmods.dev/skills/trilwu/secskills/bypassing-mobile-pinning"><img src="https://agentmods.dev/badge/skills/trilwu/secskills/bypassing-mobile-pinning.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 99 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,587 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 1 finding, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Privilege Escalation · line 68
    Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.
    Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
How audits are shown
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 5.1 $0.00099 $0.02587
Opus 5 $0.00049 $0.01293
Sonnet 5 $0.00020 $0.00517
Haiku 4.5 $0.00010 $0.00259

Measured 7d ago against content hash 808fcf7a94cc, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

bypassing-mobile-pinning scanned grade A with 1 finding 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 7d 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.

Asks for rootlowPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

adb shell chmod 644 /system/etc/security/cacerts/9a5ba580.0

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

secskills-offense/skills/bypassing-mobile-pinning/SKILL.md · 214 lines

How it starts

The opening of the file, as written. The whole thing — 214 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Bypassing Mobile Pinning

Most time lost here is spent bypassing pinning that was never there. An empty proxy has at least six causes, and the fix for each is different — one of them is not pinning at all but Android's default distrust of user CAs, and another is that the app has its own TLS stack and never saw your proxy. Diagnose before you reach for a bypass script.

Use only against apps you are authorized to test.

When to Use

  • Burp/mitmproxy/Charles shows a TLS handshake failure from a mobile app
  • The proxy shows nothing while the app clearly reaches the network
  • The app reports "network error", "connection insecure", or similar with the proxy configured
  • You know the target pins, and need the right hook for its stack

When NOT to Use

  • Flutter targets — use reversing-flutter-apps; Flutter's failure looks identical but the cause and fix are specific to its engine
  • The wider mobile assessment — use testing-mobile-applications
  • The backend once traffic is visible — use testing-apis
  • Reversing a native .so in depth — use analyzing-binaries

Diagnose First

Run this before installing anything. The symptom tells you the cause.

Symptom Likely cause Fix
Proxy sees the CONNECT, then TLS alert unknown_ca / bad_certificate Your CA is not trusted Install as system CA, or patch Network Security Config
Proxy sees the CONNECT, then alert only for some domains Real pinning, scoped to those hosts Hook the pinning check
Proxy sees nothing at all, app works App ignores the system proxy Force traffic at the network layer (Flutter, gRPC, some SDKs)
Proxy sees the handshake, server rejects the client Mutual TLS — the app presents a client certificate Extract the client cert; this is not pinning
Works on emulator, fails on device (or vice versa) Root/emulator detection, not TLS Different problem — see the detection section
Fails only after login Pinning applied to the API host only Hook, then re-check

Read the full file on GitHub · 214 lines

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. 7d ago First seen · 214 lines · 99 tokens per session scan A 808fcf7a94cc

Subscribe to this mod's changes

bypassing-mobile-pinning is a skill published in the GitHub repository trilwu/secskills (138 stars, last pushed 7d ago), licensed MIT. It adds 99 tokens to every session and 2,587 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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