diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 36d3eac..58544ae 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,14 +6,18 @@ on:
   pull_request:
   workflow_dispatch:
 
+permissions: {}
+
 # Teaching material rather than a published package: there is no test suite, so
 # CI verifies that dependencies install and every source file parses.
 jobs:
   check:
+    permissions:
+      contents: read
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
-      - uses: actions/setup-node@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
         with:
           node-version: '22'
       - run: npm install --no-audit --no-fund
diff --git a/.github/workflows/security-audit.yml b/.github/workflows/security-audit.yml
index b218b03..3f4fbaa 100644
--- a/.github/workflows/security-audit.yml
+++ b/.github/workflows/security-audit.yml
@@ -14,9 +14,7 @@ on:
     - cron: '17 6 * * 1'
   workflow_dispatch:
 
-permissions:
-  contents: read
-  issues: write
+permissions: {}
 
 concurrency:
   group: security-audit-${{ github.ref }}
@@ -24,10 +22,13 @@ concurrency:
 
 jobs:
   audit:
+    permissions:
+      contents: read
+      issues: write
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
-      - uses: actions/setup-node@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
         with:
           node-version: 22
       # Some repos intentionally ship without a committed lockfile; `npm ci`
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..efdc598
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2018 Mark Stuart
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.