Can't find variable: gmo →  Google Chromeのバグ？

弊社が開発運用しているWebアプリケーションでは、Javascriptエラーをサーバーサイドに通知・記録しているのですが、2025年2月7日から突然以下のJavascriptエラーが大量に発生するようになりました。

ユーザーエージェントで`group by`したところすべてが`iOS上のGoogleアプリ`です。（後述）
（iOSだけで発生するJavascriptエラー多いんですよね…。）

```
Can't find variable: gmo
```

弊社システムを導入しているすべての地域で観察されています。

この事象は、世界中で発生していてあちこちでレポートされるようになりました。どうやら`Google Chrome`の不具合のようです。`chromium`のissuesにも報告されています。

- [Google search app causing "Can't find variable: gmo" error on websites [396043331] - Chromium](https://issues.chromium.org/issues/396043331)
- [reactjs - Sentry errors "variable not found: gmo", "invalid or unexpected token" due to google ads snippet in index.html of our react app - Stack Overflow](https://stackoverflow.com/questions/79434372/sentry-errors-variable-not-found-gmo-invalid-or-unexpected-token-due-to-go)
- [ReferenceError: Can't find variable: gmo · Issue #65 · The-Best-Codes/bestcodes-react-site](https://github.com/The-Best-Codes/bestcodes-react-site/issues/65)

## 参考/問題が発生しているUserAgent

|UA|発生回数|
|-|:-:|
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 1161 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 1032 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 785 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 336 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 17_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 243 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 227 |
| Mozilla/5.0 (iPad; CPU OS 18_3_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 124 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 16_7_10 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 94 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 17_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 78 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_2_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 67 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 16_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 63 |
| Mozilla/5.0 (iPad; CPU OS 18_3_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 56 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 56 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_2_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 47 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 16_7_10 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 46 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 17_3_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 28 |
| Mozilla/5.0 (iPad; CPU OS 17_6_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 15 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_2_0 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 14 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 17_5_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 13 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 18_0_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 12 |
| Mozilla/5.0 (iPad; CPU OS 17_7_5 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 11 |
| Mozilla/5.0 (iPad; CPU OS 18_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 11 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 16_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 11 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 16_3_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/355.0.723646882 Mobile/15E148 Safari/604.1 | 11 |
| Mozilla/5.0 (iPad; CPU OS 18_1_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 10 |
| Mozilla/5.0 (iPhone; CPU iPhone OS 17_7_1 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) GSA/354.0.720749604 Mobile/15E148 Safari/604.1 | 10 |