An issue fork is a temporary repository for working on source code changes for an issue. It starts out as a copy of the main repository for the project, but it allows all community members to commit and push changes.
From the drupal.org issue page, you create an issue fork by clicking the Create issue fork button below the issue summary:
Most work in the Drupal open-source project and community is organized around issues (see Overview of projects and issues and Life Cycle of an Issue for background). So a first step, if you want to contribute, is often to find an issue to work on. Here are some tips and suggestions for finding an issue to work on.
Most changes in Drupal software, as well as some changes in Drupal documentation and community policies and procedures, are discussed, decided upon, and enacted through the use of issues, each of which is associated with a particular project. This page provides a summary of the typical phases an issue goes through, although not all issues go through all of these phases. The phases have accompanying changes to various fields on issues, especially the Status field.
Issues that are about documentation need different information from issues about software. This issue summary template should help make sure the right information is on the issue.
If you discover a vulnerability in Drupal core or contributed project (module, theme, or distribution) that is covered by the Security Advisory policy, keep it confidential.
There are two ways to report:
1. Report directly on Drupal's confidential issue tracker (preferred)