OWASP Cheat Sheet Series: Application Security Reference
/CheatSheetSeries
OWASP Cheat Sheet Series earns a spot in your bookmarks: each entry is short enough to read during a code review and specific enough to act on immediately. It won't explain why a vulnerability class exists in the first place, but as a checklist to consult while writing authentication or input-validation code, it beats scrolling through blog posts of unknown vintage.
What the OWASP Cheat Sheet Series is
OWASP Cheat Sheet Series is a GitHub repository of markdown files, one file per application-security topic, published by the OWASP Foundation and edited by named project leaders and a core team rather than an anonymous wiki. The repo is the editorial source only; the README says this markdown isn't meant to be cited directly, and points readers to the built site at cheatsheetseries.owasp.org instead.
Why this security reference is indispensable
The project didn't start on GitHub. Its content began on the OWASP wiki between 2014 and 2018, tracked here as V1, then moved to this repository from 2019 onward as V2 — so what you're reading has already survived one platform migration and years of pull-request review instead of being written once and abandoned. Governance is named, not anonymous: three project leaders and a small core team are listed in the README, plus a public Slack channel for questions. That combination — a defined editorial team, a documented contribution guideline, and markdown/terminology linting enforced before a merge — is what keeps individual entries from drifting into contradictory advice the way an open wiki tends to.
Security cheat sheets by topic
- ✓Each cheat sheet is a single markdown file scoped to one application-security topic, not a general security handbook chapter.
- ✓GUIDELINE.md defines how to structure a new cheat sheet, so entries follow a consistent format instead of each contributor's own style.
- ✓npm run lint-markdown and npm run lint-terminology run before changes merge, catching formatting and terminology inconsistencies.
- ✓The rendered reference lives at cheatsheetseries.owasp.org; the GitHub repo is markdown source, not the intended reading surface.
- ✓A ZIP bundle of the built site is downloadable for offline reference.
- ✓You can build and preview the site yourself locally via make generate-site and make serve, or inside a Docker or Podman container.
How developers use these cheat sheets
- •Pulling up the relevant sheet mid security code review to check whether a session-management or input-validation pattern matches documented practice.
- •Using one cheat sheet as onboarding material so a new engineer gets OWASP-sourced guidance instead of whatever the last hire happened to remember.
- •Referencing a specific topic while threat modeling a new feature, before deciding which controls actually need to be built.
- •Citing the official site's URL for a topic inside an internal security policy document, rather than restating advice from memory.
- •Building the site locally to preview a fix or a new entry before opening a pull request against it.
Strengths
- ✓Named, accountable maintainers (project leaders and a core team listed in the README) instead of an anonymous wiki anyone can silently edit.
- ✓A documented contribution guideline plus markdown/terminology linting keeps entries in a consistent format rather than each one reading differently.
- ✓Free to use under CC-BY-SA-4.0, with an offline ZIP bundle available if you don't want to depend on the live site.
- ✓Survived a real migration: years of content moved from the OWASP wiki (2014-2018) to this GitHub repo (2019 onward) instead of being abandoned.
What the series does not cover
- △The README itself warns the markdown files aren't meant to be referenced externally — you have to go through the built website, an extra hop if you expected to link straight to a GitHub file.
- △Content is licensed CC-BY-SA-4.0, a share-alike license, so reusing or adapting cheat sheet text in an internal or commercial document carries an attribution and same-license obligation, not a no-strings copy-paste.
- △There's no visible per-entry changelog or last-updated date in the repo metadata, so judging how current a given cheat sheet is means checking its own file history.
- △It's reference material, not training: reading a cheat sheet tells you the correct pattern, it doesn't verify your implementation actually follows it.
Other application security resources
Who benefits most from these cheat sheets
Developers who already know roughly what they're implementing — authentication, file upload, CORS — and want a concrete do/don't list for that topic get the most out of this. Security champions embedding practices into a team's definition of done can point at a specific sheet instead of writing their own web security checklist from scratch. It's less useful as a first introduction to security concepts for someone who doesn't yet know which topic they need.
Frequently asked questions
OWASP Cheat Sheet Series is published under the CC-BY-SA-4.0 license, so it's free to read and reuse, but that license requires attribution and share-alike terms if you redistribute or adapt the content — check it before copying text into a commercial document.
The GitHub metadata for OWASP Cheat Sheet Series doesn't list specific programming languages or frameworks — the repository is organized by application-security topic rather than by language, so which frameworks a given sheet touches only becomes clear once you open that sheet.
Update frequency isn't documented in the repository metadata or README. OWASP Cheat Sheet Series is maintained through ongoing pull requests from contributors and a core team, but no changelog or cadence is published at the repo level — check an individual file's commit history for its own timeline.
OWASP Cheat Sheet Series does take outside contributions: the README points to a CONTRIBUTING.md guide and a separate GUIDELINE.md that explains how to structure a new cheat sheet, plus open GitHub issues you can pick up and submit a pull request against.
OWASP Top 10 is a short, prioritized list of the biggest web application risk categories, while OWASP Cheat Sheet Series is a much larger collection of per-topic, how-to-fix documents. Think of the Top 10 as naming the risk and the cheat sheets as the implementation-level guidance for addressing it.
The GitHub metadata and README for OWASP Cheat Sheet Series don't describe the OWASP Developer Guide or draw a direct comparison to it, so any specific difference between the two projects isn't documented here — check each project's own page for how it defines its scope.
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