GitHub Commits Skipping Workflows

Severity: medium
Log types: GitHub.Webhook
Tags: CI/CD, Workflow
Reference: https://docs.github.com/en/actions/managing-workflow-runs/skipping-workflow-runs
Source: github.com/panther-labs/panther-analysis

Detects commits from cross-fork scenarios that contain workflow skip directives, which bypass GitHub Actions workflows. These skip patterns ([skip ci], [ci skip], [no ci], [skip actions], [actions skip], skip-checks:true) can be used to avoid security checks and CI/CD processes. This rule only alerts on commits to public forkable repositories.

MITRE ATT&CK coverage

Tactic	Techniques
Initial Access	`T1195.002` Supply Chain Compromise: Compromise Software Supply Chain
Stealth	`T1622` Debugger Evasion

Rule body yaml

AnalysisType: rule
Filename: github_workflow_skip_commits.py
RuleID: "GitHub.Webhook.WorkflowSkipCommits"
DisplayName: "GitHub Commits Skipping Workflows"
Enabled: true
LogTypes:
  - GitHub.Webhook
Reports:
  MITRE ATT&CK:
    - TA0001:T1195.002  # Supply Chain Compromise: Compromise Software Supply Chain
    - TA0005:T1622  # Defense Evasion: Debugger Evasion
Tags:
  - CI/CD
  - Workflow
Severity: Medium
Description: >
  Detects commits from cross-fork scenarios that contain workflow skip directives, which bypass GitHub Actions workflows.
  These skip patterns ([skip ci], [ci skip], [no ci], [skip actions], [actions skip], skip-checks:true)
  can be used to avoid security checks and CI/CD processes. This rule only alerts on commits to public forkable repositories.
Runbook: >
  1. Review the commit message and author to determine if the workflow skip was intentional and authorized
  2. Verify that skipping workflows is appropriate for the type of changes made
  3. Check if the repository has policies requiring workflow runs for certain changes
  4. Consider if the skip bypasses important security or quality checks
  5. Monitor for patterns of excessive workflow skipping that might indicate policy circumvention
Reference: https://docs.github.com/en/actions/managing-workflow-runs/skipping-workflow-runs
Tests:
  - Name: Public Forkable Repo with Skip CI Pattern
    ExpectedResult: true
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "id": 123456789,
          "name": "test-repo",
          "full_name": "org/test-repo",
          "private": false,
          "allow_forking": true,
          "owner": {
            "login": "org"
          }
        },
        "commits": [
          {
            "id": "abc123",
            "message": "Fix documentation [skip ci]",
            "author": {
              "name": "Developer",
              "email": "dev@example.com"
            }
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Public Forkable Repo with Case Insensitive Skip Pattern
    ExpectedResult: true
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/feature",
        "repository": {
          "id": 123456789,
          "name": "test-repo",
          "full_name": "org/test-repo", 
          "private": false,
          "allow_forking": true
        },
        "commits": [
          {
            "id": "def456",
            "message": "Update config [SKIP CI]"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Public Forkable Repo with Multiple Skip Patterns
    ExpectedResult: true
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "private": false,
          "allow_forking": true,
          "full_name": "org/test-repo"
        },
        "commits": [
          {
            "id": "ghi789",
            "message": "Regular commit"
          },
          {
            "id": "jkl012",
            "message": "Minor fix [ci skip]"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Private Repo with Skip CI Pattern (Should Not Alert)
    ExpectedResult: false
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "private": true,
          "allow_forking": true,
          "full_name": "org/private-repo"
        },
        "commits": [
          {
            "id": "private123",
            "message": "Internal change [skip ci]"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Public Repo with Forking Disabled and Skip CI (Should Not Alert)
    ExpectedResult: false
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "private": false,
          "allow_forking": false,
          "full_name": "org/no-fork-repo"
        },
        "commits": [
          {
            "id": "nofork123",
            "message": "Change [skip ci]"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Public Forkable Repo without Skip Patterns (Should Not Alert)
    ExpectedResult: false
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "private": false,
          "allow_forking": true,
          "full_name": "org/test-repo"
        },
        "commits": [
          {
            "id": "clean123",
            "message": "Add new feature with tests"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Non-Push Event with Skip Pattern (Should Not Alert)
    ExpectedResult: false
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "pull_request": {
          "id": 123,
          "title": "Fix bug [skip ci]"
        },
        "repository": {
          "private": false,
          "allow_forking": true,
          "full_name": "org/test-repo"
        },
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Public Forkable Repo with Skip Actions Pattern
    ExpectedResult: true
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "private": false,
          "allow_forking": true,
          "full_name": "org/test-repo"
        },
        "commits": [
          {
            "id": "actions123",
            "message": "Update README [skip actions]"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Public Forkable Repo with Skip Checks Trailer
    ExpectedResult: true
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "private": false,
          "allow_forking": true,
          "full_name": "org/test-repo"
        },
        "commits": [
          {
            "id": "trailer123",
            "message": "Minor typo fix\n\nskip-checks: true"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }
  - Name: Public Forkable Repo with No CI Pattern
    ExpectedResult: true
    Log:
      {
        "pusher": {
          "name": "Developer",
          "email": "dev@example.com"
        },
        "ref": "refs/heads/main",
        "repository": {
          "private": false,
          "allow_forking": true,
          "full_name": "org/test-repo"
        },
        "commits": [
          {
            "id": "noci123",
            "message": "Documentation update [no ci]"
          }
        ],
        "p_log_type": "GitHub.Webhook"
      }

Detection logic

Condition

pusher is_not_null
not (repository.private is_not_null or repository.allow_forking is_null)

This rule also runs imperative logic the parser cannot express as a filter; the conditions above are the structured part it could extract.

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`repository.allow_forking`	is_null	(no value, null check)
`repository.private`	is_not_null	(no value, null check)

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`pusher`	is_not_null	(no value, null check)

Output fields

Fields the rule emits when it matches. Chronicle authors list these in the outcome block; they appear on the detection and $risk_score drives alerting. Sentinel / Defender XDR rules build them up through project / summarize / extend stages. Sentinel maps these into alert fields via entityMappings and customDetails; Defender XDR custom detections surface them as alert fields directly.

Field	Source
`action`
`actor`
`actor_location`	`actor_location.country_code`
`org`
`repo`
`user`
`full_name`	`repository.full_name`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)