GitHub CLI: GitHub Actions log output in `gh run view` allows terminal escape sequence injection

### Summary A security vulnerability has been identified in GitHub CLI that could allow terminal escape sequence injection when users view GitHub Actions workflow logs using `gh run view --log` or `gh run view --log-failed`. ### Details The vulnerability stems from the way GitHub CLI handles raw Actions log output. The `gh run view --log` and `gh run view --log-failed` commands stream workflow log lines to stdout or the configured pager without sanitizing terminal control sequences. An attacker who can influence GitHub Actions log content, for example via a PR triggered workflow, can embed escape sequences that are replayed in the user's terminal when they inspect the run. Depending on the victim's terminal emulator, injected sequences could change the window title, manipulate on screen content, or in some terminal emulators (such as `screen`) potentially execute arbitrary commands. In `2.92.0`, GitHub CLI sanitizes terminal control sequences in Actions log output before writing to the terminal. ### PoC Create a workflow that emits terminal escape sequences in its log output: ```yaml name: Escape Sequence PoC on: workflow_dispatch: jobs: emit-escape-sequences: runs-on: ubuntu-latest steps: - name: Emit terminal escape sequences run: | # OSC title set printf 'ESCAPE_MARKER_START \033]0;HIJACKED_TITLE\007 ESCAPE_MARKER_END\n' # CSI color printf 'ESCAPE_MARKER_START \033[31mRED_TEXT\033[0m ESCAPE_MARKER_END\n' # Screen title set (enables command execution in screen terminal) printf 'ESCAPE_MARKER_START \033k;malicious command;\033\\ ESCAPE_MARKER_END\n' ``` Then trigger the workflow and view its logs: ```bash gh workflow run 'Escape Sequence PoC' gh run view <run_id> --log ``` On vulnerable versions, the raw ESC bytes (0x1b) are passed through to the terminal unsanitized. On `2.92.0` and later, escape sequences are stripped and only the safe visible text is displayed. ### Impact An attacker who can control GitHub Actions workflow output can inject terminal escape sequences into a maintainer's terminal session when they inspect the run with `gh run view --log` or `gh run view --log-failed`. The practical impact depends on the victim's terminal emulator. ### Remediation and Mitigation 1. Upgrade `gh` to `2.92.0` 2. Pipe log output through a sanitizer (e.g., `gh run view --log | cat -v`) as a workaround on older versions 3. Exercise caution when viewing logs from untrusted workflow runs