Recaptcha api2/clr请求错误指向我方服务器致大量404问题求助

最近数日，我方服务器收到的404请求数量持续增长，所有请求格式完全一致（部分内容已脱敏）：

1.1.1.1 - - [11/Jul/2024:14:00:56 +0000] "POST /recaptcha/api2/clr?k={our_site_key} HTTP/1.1" 404 5126 "https://{some_url_on_our_site}" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.5 Safari/605.1.15"
2.2.2.2 - - [11/Jul/2024:14:16:46 +0000] "POST /recaptcha/api2/clr?k={our_site_key} HTTP/1.1" 404 1698 "https://{some_url_on_our_site}" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36 Edg/126.0.0.0"
3.3.3.3 - - [11/Jul/2024:18:08:07 +0000] "POST /recaptcha/api2/clr?k={our_site_key} HTTP/1.1" 404 1698 "https://{some_url_on_our_site}" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36"
4.4.4.4 - - [11/Jul/2024:18:13:37 +0000] "POST /recaptcha/api2/clr?k={our_site_key} HTTP/1.1" 404 1698 "https://{some_url_on_our_site}" "Mozilla/5.0 (Linux; Android 10; K) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Mobile Safari/537.36"
5.5.5.5 - - [11/Jul/2024:19:11:10 +0000] "POST /recaptcha/api2/clr?k={our_site_key} HTTP/1.1" 404 1698 "https://{some_url_on_our_site}" "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:127.0) Gecko/20100101 Firefox/127.0"
6.6.6.6 - - [11/Jul/2024:19:47:14 +0000] "POST /recaptcha/api2/clr?k={our_site_key} HTTP/1.1" 404 1150 "https://{some_url_on_our_site}" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/126.0.0.0 Safari/537.36"

关键现象总结：

• 请求来自多种设备和浏览器，无明显单一特征
• 目标URL/recaptcha/api2/clr?k={our_site_key}本应指向Google服务器，我方服务器不存在该路径
• 我方长期未修改Recaptcha v2 Invisible的集成方式，且无法自行复现该问题
• 请求频率正持续上升
• 捕获到的请求体（php://input）为加密二进制数据，尝试用Google公钥和私钥均无法解密

现寻求技术同仁帮忙分析问题原因。

内容的提问来源于stack exchange，提问作者IncredibleHat