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Free program analysis focused on bugs that matter to you.

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Find Python web-app bugs delightfully fast, without changing your workflow

Installation · Motivations · Code Checks · Usage
Workflows · Integrations · Help & Community

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Inspired by tools like the ESLint plugin for React, Bento was created for Flask and Django. With Bento you’ll:

  • Find bugs that matter. Checks find security and reliability bugs in your code. They’re vetted across thousands of open source projects and never nit your style.
  • Upgrade your tooling. You don’t have to fix existing bugs to adopt Bento. It’s diff-centric, finding new bugs introduced by your changes. And there’s zero config.
  • Go delightfully fast. Run Bento automatically locally or in CI. Either way, it runs offline and never sends your code anywhere.

Demonstrating Bento running in a terminal


Bento is free and requires Python 3.6+ and Docker 19.03+. It runs on macOS and Linux.

In a Git project directory:

$ pip3 install bento-cli && bento init

Go forth and write great code!


See our Bento introductory blog post to learn the full story.

Bento is part of a quest to make world-class security and bugfinding available to all developers, for free. We’ve learned that most developers have never heard of—let alone tried—tools that find deep flaws in code: like Codenomicon, which found Heartbleed, or Zoncolan at Facebook, which finds more top-severity security issues than any human effort. These tools find severe issues and also save tons of time, identifying hundreds of thousands of issues before humans can. Bento is a step towards universal access to tools like these.

We’re also big proponents of opinionated tools like Black and Prettier. This has two implications: Bento ignores style-related issues and the bikeshedding that comes with them, and it ships with a curated set of checks that we believe are high signal and bug-worthy. See Three things your linter shouldn’t tell you for more about our decision making process.

Code Checks

Bento’s check focus on security and reliability bugs in Flask and Django projects.

Flask Jinja Django
missing JWT token href template variable coming soon
secure set cookie missing noopener
send file open missing noreferrer Docker
unescaped file extension missing csrf protection Hadolint
use blueprint for modularity missing doctype
use jsonify meta charset Shell
avoid hardcoded config meta content-type ShellCheck
unquoted attribute template variable
no auth over http SQLAlchemy
use scheme coming soon
use timeout

See the full list of Bento’s specialty checks.


Out-of-the-box, Bento is configured for your personal use. See Team Use to setup Bento for all contributors.


$ pip3 install --upgrade bento-cli

Command Line Options

$ bento --help
Usage: bento [OPTIONS] COMMAND [ARGS]...

  -h, --help    Show this message and exit.
  --version     Show the version and exit.
  --agree       Automatically agree to terms of service.
  --email TEXT  Email address to use while running this command without global
                configs e.g. in CI

  archive  Suppress current findings.
  check    Checks for new findings.
  disable  Turn OFF a Bento feature for this project.
  enable   Turn ON a Bento feature for this project.
  init     Autodetects and installs tools.

  To get help for a specific command, run `bento COMMAND --help`

Exit Codes

bento check may exit with the following exit codes:

  • 0: Bento ran successfully and found no errors
  • 2: Bento ran successfully and found issues in your code
  • 3: Bento or one of its underlying tools failed to run


Individual Use

Bento understands the importance of getting out of the way so you can write your code. It runs at commit-time on your diffs and only affects you; it won’t change anything for other project contributors or modify Git state.

Initialization enables autorun behind the scenes. By default autorun blocks the commit if Bento returns findings. To make it non-blocking:

$ bento enable autorun --no-block

You can always manually run Bento on staged files or directories via:

$ bento check [PATHS]

This will show only new findings introduced by these files AND that are not in the archive (.bento/archive.json). Use --all to check all Git tracked files, not just those that are staged:

$ bento check --all [PATHS]

This feature makes use of Git hooks. If the Bento hook incorrectly blocks your commit, you can skip it by passing the --no-verify flag to Git at commit-time (please use this sparingly since all hooks will be skipped):

$ git commit --no-verify

Team Use

Running Locally

To setup Bento for all project contributors, add Bento’s configuration to Git (it’s ignored by default):

# Add Bento's cache to the project's .gitignore
$ echo ".bento/cache" >> .gitignore
# Commit Bento's config to your project
$ git add --force .bento .bentoignore

Contributors can run Bento for themselves using the project’s configuration via:

$ bento init

Running in CI/CD

Bento has first-class support for checking pull requests with GitHub Actions. Such checks will report only on the bugs introduced by the changes in the pull request.

To get started, just run bento enable ci in your project directory. This will add a CI configuration file to your repository.

Advanced CI/CD configuration

You can also configure Bento in CI to analyze your entire project, instead of only the changes from a pull request. So that you don’t have to fix all existing issues before making Bento blocking, its archive feature allows historical issues to be tracked and ignored during CI.

To use the archive feature so Bento returns a non-zero exit code only for new issues, rather than all existing issues, first create the archive:

$ bento archive .

Commit Bento’s configuration to the project:

# Add Bento's cache to the project's .gitignore
$ echo ".bento/cache" >> .gitignore
# Commit Bento's config to your project
$ git add --force .bento .bentoignore

You can then add Bento to your CI scripts:

$ pip3 install bento-cli && bento --version
$ bento --agree --email=<YOUR_EMAIL> check --all 2>&1 | cat

We pipe through cat to disable Bento's interactive tty features (e.g. progress bars, using a pager for many findings).

If you use CircleCI, the above commands become:

version: 2.1

  executor: circleci/python:3.7.4-stretch-node
    - checkout
    - run:
        name: "Install Bento"
        command: pip3 install bento-cli && bento --version
    - run:
        name: "Run Bento check"
        command: bento --agree --email=<YOUR_EMAIL> check --all 2>&1 | cat

bento check will exit with a non-zero exit code if it finds issues in your code (see Exit Codes).

If you need help setting up Bento with another CI provider please open an issue. Documentation PRs welcome if you set up Bento with a CI provider that isn’t documented here!

Help and Community

Need help or want to share feedback? We’d love to hear from you!

We’re constantly shipping new features and improvements.

We’re fortunate to benefit from the contributions of the open source community and great projects such as Bandit, ESLint, Flake8, and their plugins. 🙏

License and Legal

Please refer to the terms and privacy document.

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Copyright (c) r2c.

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