WordPressの管理画面にログインし、左メニュー「プラグイン」（またはテーマ）に Rank Math SEO PRO があるか確認します。
あれば、バージョン番号を見て「subset of version 3.0.123 packages downloaded or updated between October 15, 2026 at 20:02 UTC and October 16, 2026 at 07:12 UTC」に当てはまるか確認します。
Rank Math SEO PRO for WordPress is affected by a supply-chain compromise in a subset of version 3.0.123 packages downloaded or updated between October 15, 2026 at 20:02 UTC and October 16, 2026 at 07:12 UTC. Rank Math states that the affected plugin files contained malware that could compromise a website if the plugin was activated and directs sites that activated an affected package to treat the website as compromised. The malware may establish persistent access, communicate with rank1cdn[.]com, recreate hidden backdoors on page visits, and expose WordPress credentials, database credentials, API keys, and other secrets accessible to the web server. Rank Math identifies three malicious wp_options keys, hidden PHP backdoors, unauthorized administrator accounts, a fake WordPress core file, PHP-executable .cache files, and a system cron marker as incident indicators. Only packages obtained during the vendor-confirmed window are claimed as affected; version 3.0.123 alone is not sufficient to establish compromise. Rank Math removed the affected files and released version 3.0.124 as the clean replacement.