fix: restrict BEGIN_COMMIT_OVERRIDE to PR authors with write access

src/commit.ts

@@ -453,9 +453,25 @@ export function parseConventionalCommits(
   return conventionalCommits;
 }
 
+// Author associations whose BEGIN_COMMIT_OVERRIDE body section is honored.
+// Only roles that already have write access to the repository are trusted:
+// the PR body of a merged PR remains editable by its author indefinitely,
+// so honoring overrides from contributor/first-time-contributor/none would
+// let an external contributor rewrite their merged commit message (and the
+// resulting CHANGELOG / release notes) after review has completed.
+const TRUSTED_OVERRIDE_ASSOCIATIONS = new Set<string>([
+  'OWNER',
+  'MEMBER',
+  'COLLABORATOR',
+]);
+
 function preprocessCommitMessage(commit: Commit): string {
   // look for 'BEGIN_COMMIT_OVERRIDE' section of pull request body
   if (commit.pullRequest) {
+    const association = commit.pullRequest.authorAssociation;
+    if (!association || !TRUSTED_OVERRIDE_ASSOCIATIONS.has(association)) {
+      return commit.message;
+    }
     const overrideMessage = (
       commit.pullRequest.body.split('BEGIN_COMMIT_OVERRIDE')[1] || ''
     )

src/github.ts

@@ -112,6 +112,7 @@ interface GraphQLPullRequest {
       hasNextPage: boolean;
     };
   };
+  authorAssociation?: string;
 }
 
 interface CommitHistory {
@@ -265,6 +266,7 @@ export class GitHub implements Scm {
                         }
                       }
                       body
+                      authorAssociation
                       mergeCommit {
                         oid
                       }
@@ -382,6 +384,8 @@ export class GitHub implements Scm {
           body: pullRequest.body,
           labels: pullRequest.labels.nodes.map(node => node.name),
           files: (pullRequest.files?.nodes || []).map(node => node.path),
+          authorAssociation:
+            pullRequest.authorAssociation as PullRequest['authorAssociation'],
         };
       }
       if (mergePullRequest) {

src/pull-request.ts

@@ -12,6 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+export type PullRequestAuthorAssociation =
+  | 'OWNER'
+  | 'MEMBER'
+  | 'COLLABORATOR'
+  | 'CONTRIBUTOR'
+  | 'FIRST_TIME_CONTRIBUTOR'
+  | 'FIRST_TIMER'
+  | 'MANNEQUIN'
+  | 'NONE';
+
 export interface PullRequest {
   readonly headBranchName: string;
   readonly baseBranchName: string;
@@ -22,4 +32,5 @@ export interface PullRequest {
   readonly labels: string[];
   readonly files: string[];
   readonly sha?: string;
+  readonly authorAssociation?: PullRequestAuthorAssociation;
 }

test/commits.ts

@@ -207,6 +207,7 @@ describe('parseConventionalCommits', () => {
       labels: [],
       files: [],
       body,
+      authorAssociation: 'MEMBER',
     };
 
     const conventionalCommits = parseConventionalCommits([commit]);
@@ -227,6 +228,7 @@ describe('parseConventionalCommits', () => {
       labels: [],
       files: [],
       body,
+      authorAssociation: 'OWNER',
     };
 
     const conventionalCommits = parseConventionalCommits([commit]);
@@ -237,6 +239,48 @@ describe('parseConventionalCommits', () => {
     expect(conventionalCommits[1].bareMessage).to.eql('another feature');
   });
 
+  it('ignores BEGIN_COMMIT_OVERRIDE from an untrusted PR author', async () => {
+    const commit = buildMockCommit('chore: some commit');
+    const body =
+      'BEGIN_COMMIT_OVERRIDE\nfix!: forged fix\n\nBREAKING CHANGE: forged\nEND_COMMIT_OVERRIDE';
+    commit.pullRequest = {
+      headBranchName: 'fix-something',
+      baseBranchName: 'main',
+      number: 123,
+      title: 'chore: some commit',
+      labels: [],
+      files: [],
+      body,
+      authorAssociation: 'CONTRIBUTOR',
+    };
+
+    const conventionalCommits = parseConventionalCommits([commit]);
+    expect(conventionalCommits).lengthOf(1);
+    expect(conventionalCommits[0].type).to.eql('chore');
+    expect(conventionalCommits[0].bareMessage).to.eql('some commit');
+    expect(conventionalCommits[0].breaking).to.be.false;
+    expect(conventionalCommits[0].notes).lengthOf(0);
+  });
+
+  it('ignores BEGIN_COMMIT_OVERRIDE when authorAssociation is missing', async () => {
+    const commit = buildMockCommit('chore: some commit');
+    const body = 'BEGIN_COMMIT_OVERRIDE\nfix: forged fix\nEND_COMMIT_OVERRIDE';
+    commit.pullRequest = {
+      headBranchName: 'fix-something',
+      baseBranchName: 'main',
+      number: 123,
+      title: 'chore: some commit',
+      labels: [],
+      files: [],
+      body,
+    };
+
+    const conventionalCommits = parseConventionalCommits([commit]);
+    expect(conventionalCommits).lengthOf(1);
+    expect(conventionalCommits[0].type).to.eql('chore');
+    expect(conventionalCommits[0].bareMessage).to.eql('some commit');
+  });
+
   it('handles a special commit separator', async () => {
     const commits = [buildCommitFromFixture('multiple-commits-with-separator')];
     const conventionalCommits = parseConventionalCommits(commits);

test/manifest.ts

@@ -3029,6 +3029,7 @@ describe('Manifest', () => {
             labels: [],
             files: [],
             sha: 'abc123',
+            authorAssociation: 'MEMBER',
           },
         },
         {