GitHub API: Repositories Contributed To

With GraphQL API v4, you can now get these contributed repo using :

{
  viewer {
    repositoriesContributedTo(first: 100, contributionTypes: [COMMIT, ISSUE, PULL_REQUEST, REPOSITORY]) {
      totalCount
      nodes {
        nameWithOwner
      }
      pageInfo {
        endCursor
        hasNextPage
      }
    }
  }
}

Try it in the explorer

If you have more than 100 contributed repo (including yours), you will have to go through pagination specifying after: "END_CURSOR_VALUE" in repositoriesContributedTo for the next request.