Hidden Text Detector

Detects hidden text and manipulation attempts in PDF and DOCX documents - white-on-white text, sub-legible fonts, text positioned off-page, invisible render mode, Word's hidden attribute, and invisible Unicode characters. Use when the user asks "does this document contain hidden text", "check this contract for hidden clauses", "is someone trying to manipulate me", "scan this PDF for prompt injection", "is this a scam", or BEFORE analysing any contract, quote, invoice, or document received from an external party.

9 stars 1 forksDocuments & Office Files

Install

skills CLI (Claude Code, Cursor, Codex and more)

npx skills add wppoland/hidden-text-detector --skill hidden-text-detector

Manual install

git clone --depth 1 https://github.com/wppoland/hidden-text-detector.git /tmp/hidden-text-detector
mkdir -p ~/.claude/skills
cp -r /tmp/hidden-text-detector/. ~/.claude/skills/hidden-text-detector

Personal skills live in ~/.claude/skills. Use .claude/skills in a project folder to share a skill with your team.

From the SKILL.md

# Hidden Text Detector

Documents from third parties can carry content that is invisible to a human
reader but still fully present in the file, and therefore read by AI
assistants, by copy-paste, and by text extraction. It is used to steer a
reviewer's judgement, to smuggle instructions to an AI agent, or to bury
contractual language the counterparty will never see.

## When to run

Run the scan **before** analysing the content of any document that came from
outside: contracts, quotes, invoices, RFPs, NDAs, terms of service, or
attachments from unfamiliar senders.

For your own documents or files from a trusted source the scan is unnecessary
unless the user asks for it explicitly.

## How to run

```bash
python3 scripts/scan.py FILE [FILE ...]
```

JSON output for further processing:

```bash
python3 scripts/scan.py --json FILE
```

Exit code is `1` when anything CRITICAL is found, `0` otherwise, so the scan
can gate a pipeline.

Dependencies: `pymupdf` for PDF, `python-docx` for DOCX.

```bash
pip install pymupdf python-docx
```

## What it detects

**PDF: structural and visual analysis, not text analysis.** This distinction matters:
once text is extracted, hidden text looks identical to ordinary text. The
concealment lives in the rendering instructions, so that is where to look.

| Technique | Criterion |
|---|---|
| Text invisible against its background | rendered-pixel contrast below 24/255 across the text area |

Read the full skill on GitHub

Details

Skill name: hidden-text-detector
Repository: wppoland/hidden-text-detector
License: MIT
Repo updated: 28 July 2026

FAQ

What does the Hidden Text Detector skill do?

How do I install the Hidden Text Detector skill?

skills CLI (Claude Code, Cursor, Codex and more): npx skills add wppoland/hidden-text-detector --skill hidden-text-detector. Skills go in ~/.claude/skills (personal) or .claude/skills (project), and Claude loads them automatically when a task matches the description.

Is Hidden Text Detector popular?

It lives in wppoland/hidden-text-detector, which has 9 GitHub stars and 1 forks.

Related skills

Vietnamese DOCX

bGiaHuy/vietnamese-docs-style

Soạn, biên tập văn bản tiếng Việt và tạo/chỉnh sửa DOCX văn phòng, học thuật, hành chính theo mẫu phù hợp. Dùng cả khi chỉ cần đoạn văn, đề mục hoặc danh sách đánh số trong chat. Chọn thể thức theo loại văn bản và nơi tiếp nhận; chỉ áp dụng Nghị định 30/2020/NĐ-CP trong phạm vi phù hợp.

Documents & Office Files

Quarto Talks

alfredo-hs/quarto-talks

Turn source material into a restrained Quarto RevealJS talk using the quarto-talks format. Use for papers, manuscripts, documents, figures, code, bibliographies, or existing slide decks when the requested output is an argument-led presentation.

Documents & Office Files

Cugb Doctoral Thesis Format

keros68/cugb-doctoral-thesis-format

Use when editing, auditing, or finalizing CUGB doctoral thesis DOC/DOCX files, especially thesis templates, format detection reports, cover pages, declarations, abstracts, TOC, section breaks, odd/even headers, page numbers, headings, captions, formulas, punctuation, GB7714 references, and final Word submission. Covers China University of Geosciences (Beijing) (中国地质大学（北京）) doctoral dissertations (博士学位论文格式预检). Not for master's theses or other universities' templates.

Documents & Office Files

Heige Resume

HeiGeAi/HeiGe-Resume

简历锻造系统。2026 年投简历，机器在人之前先看你的简历：被关键词搜到、被 AI 按岗位打分排序，过了这关 HR 才花六到八秒扫一眼。本 skill 把同一段经历升级成既被机器排到前面、又让人记得住的简历，而不是堆一张流水账履历表。能把履历写得更高级（负责什么改写成做成了什么）、按目标岗位优化匹配度、按需要产出泛用版和特化版两份。适用场景：求职简历、跳槽简历、应届生简历、技术/产品/设计/运营简历、高管简历、自由职业者一页纸、个人主页 hero。核心方法论：一句话定位 / 履历升级 / 对岗定制 / 机器可读 / 6 秒扫描 / 一页纪律 + 反作弊体检。当用户要求"做份简历""帮我写简历""优化简历""把经历写得更高级""升级履历""按岗位/JD 优化匹配度""让简历过得了 AI 筛""做个一页纸介绍"时，必须使用此 skill。输出为单文件 HTML：A4 排版、文字可选中、可 Cmd+P 完美导出 PDF，且默认带可编辑层，用户打开就能在浏览器里直接改文字、再导出 PDF 或下载独立 HTML。动手前先定调，出货前过反作弊体检。注意：本 skill 负责"从零设计有重点、机器和人都买账的简历/一页纸"；如果是做多页演示 deck，那是 heige-ppt 的活；如果是做产品界面/落地页，那是 heige-ui 的活。

Documents & Office Files

Echo Slides Skill

xiangzhouEcho/Echo-Slides-Skill

Use when extracting slides, PPT pages, or presentation screenshots from a video or YouTube talk; when a lecture, webinar, or conference recording needs its deck recovered as images; when someone asks to turn a talk recording back into slides, pull the deck out of a video, or get the PPT from a video; or when frame-grabbing a video produces hundreds of near-identical duplicates that need deduplicating. Also triggers on Chinese phrasings such as 扒 PPT, 把视频里的幻灯片提取出来, 从演讲录像还原幻灯片.

Documents & Office Files

Excel Skill

gaaiyun/excel-skill

Generate Excel workbooks (.xlsx) with industry-specific templates for finance, FMCG, e-commerce, and internet/SaaS scenarios. Use this skill when the user wants to (1) create an Excel template with formulas, formatting, and charts; (2) build a dashboard or report; (3) analyze data with pivot tables or Power Query; (4) automate Excel generation in Python via openpyxl; (5) audit AI-generated openpyxl code for common pitfalls (formula-as-string, data_only flag misuse). Provides progressive-disclosure access to formulas, pivot tables, Power Query, charts, openpyxl, pandas-excel, and 4 industry tem

Documents & Office Files

Browse the most popular Claude skills, all documents & office files skills, or write your own with the skills generator.