Summary

Simple Icons is vulnerable to an Actions expression injection, allowing an attacker to take over the repository and steal secrets.

Details

The autoclose-issues.yml workflow is triggered on issue (i.e., when an Issue is created). The workflow starts with full write-permissions GitHub repository token since the default workflow permissions on Organization/Repository level are set to read-write.

Taking the above into account, this workflow injects data controlled by said Issue (${{ github.event.issue.title }} -- the title of the Issue) into a Run step's script, allowing an attacker to take over the GitHub Runner to run custom commands and alter the repository.

- id: match-java
  name: Match Java
  run: |
    if [[ "${{ github.event.issue.title }}" =~ (^|[[:space:]])([jJ][aA][vV][aA])([[:space:]]|$) ]]; then
        echo "match=true" >> $GITHUB_OUTPUT
    fi

This issue was found using CodeQL for JavaScript's Expression injection in Actions query.

Impact

This issue may lead to stealing workflow secrets and modification of the repository.

Proof of Concept

1. Open an Issue with the following title: $(whoami)
2. Check the workflow runs for the new Actions run that will execute the command whoami.

Resources

• CodeQL for JavaScript - Expression injection in Actions
• Keeping your GitHub Actions and workflows secure Part 2: Untrusted input
• Keeping your GitHub Actions and workflows secure Part 1: Preventing pwn requests