A simple equation challenge used as a Captcha


This plugin presents an anonymous user with a simple math addition problem on a new ticket or wiki edit page prior to submission. This presents a protection from unwanted bots making posts on your Trac website. Currently there is no customization: it picks two integers in the range of 1 - 10 and asks the user to add them together and submit the result.

Version 2.0

I'm starting to see some particular spambots get through the simple captcha, so I'm releasing version 2.0 that includes a slight modification to the format presented to the user. In addition, this version now correctly works with fcgi and mod_python by saving the Captcha information in the Trac database. To use mod_python as an example: Apache may start many processes where each has its own embedded Python interpreter. The particular Apache process that displayed the form may not be the same one that processes the form request, so there must be a persistent way to store the solution to the Captcha rather than making it easy for spambots by encoding the solution in the web page itself.

I'm also keeping a 30 day record of failed attempts in the same database, so you can get an idea of what sort of spambots are trying to get through your defenses.

For the future, it would be nice if there were multiple types of math problems presented in a way that wouldn't be easy for a bot to recognize.

Bugs/Feature Requests

Existing bugs and feature requests for MathCaptchaPlugin are here.

If you have any issues, create a new ticket.


5 / 5


2 / 2


Download the zipped source from here.


You can check out MathCaptchaPlugin from here using Subversion, or browse the source with Trac.


Install by either copying the file into your /path/to/project/environment/plugins directory, or use the following from within the source directory:

python install

Version 2.0 of the plugin creates a new database needed for processing Captchas when run using fcgi or mod_python, so you will have to run the following before you can use the plugin:

trac-admin /path/to/project/environment upgrade

Once installed and the environment is upgraded, the plugin must be enabled by adding a line to the components section in your trac.ini file:

mathcaptcha.* = enabled

Finally, give anonymous users any of the following permissions:


Anonymous users will then be prompted to solve a math problem before being allowed to submit the ticket or wiki edit, while authenticated users will not see the Captcha.

Recent Changes

17091 by rjollos on 2018-04-04 03:32:00
TracMathCaptcha 5.0dev: Fix grammar in option doc

Refs #6891.

17090 by rjollos on 2018-04-04 02:21:09
TracMathCaptcha 5.0dev: Add option ban_after_failed_attempts

This also fixes two defects that led to the number of
failures being miscounted.

Fixes #6891.

17089 by rjollos on 2018-04-04 02:00:21
TracMathCaptcha 5.0dev: Change plugin name

This prepares for publishing to pypi.

Remove the old plugin before installing:

$ pip uninstall matchcaptcha

Refs #13399.



Author: robm
Maintainer: Rob McMullen

Last modified 2 years ago Last modified on May 14, 2022, 5:50:33 AM