no-sandbox default to true

Author: owickstrom

README.md

@@ -76,7 +76,7 @@ Chrome is only installed when `driver: browser`.
 | `headers`                    | HTTP headers as multi-line `Key: Value`. See below.                                        |          |
 | `reproduce`                  | Path to a trace file to reproduce. Mutually exclusive with `time-limit` / `exit-on-violation`. |       |
 | `headless`                   | Run Chrome headless.                                                                       | `true`   |
-| `no-sandbox`                 | Disable Chromium sandboxing.                                                               | `false`  |
+| `no-sandbox`                 | Disable Chromium sandboxing. Defaults on because GitHub-hosted Ubuntu runners restrict the namespaces Chromium needs. | `true`  |
 | `chrome-version`             | Channel (`stable`, `beta`, `dev`, `canary`) or specific build ID.                          | `stable` |
 | `cache`                      | Cache the Chrome download across runs.                                                     | `true`   |
 

action.yml

@@ -69,9 +69,9 @@ inputs:
     required: false
     default: 'true'
   no-sandbox:
-    description: 'Disable Chromium sandboxing.'
+    description: 'Disable Chromium sandboxing. Defaults to `true` because GitHub-hosted Ubuntu runners restrict unprivileged user namespaces, which Chromium needs to set up its sandbox. Set to `false` on hosts with a working sandbox.'
     required: false
-    default: 'false'
+    default: 'true'
 
   # Terminal-driver options
   test-count: