I have developed a website, and I’m experiencing an issue where my client encounters a 403 Access Denied error after being logged into the admin panel for a while. Once this error occurs, they cannot access the admin panel again for a certain period.

The error seems to happen when they are editing some texts on the site. According to the server logs, the following error is recorded

7349874592942424484 176.88.108.248 80 127.0.0.1 80
–122d0000-B–
GET /favicon.ico HTTP/1.1
Connection: close
Accept: image/avif,image/webp,image/apng,image/svg+xml,image/,/*;q=0.8
Accept-Encoding: gzip, deflate, br, zstd
Accept-Language: tr-TR,tr;q=0.8
Cookie: .AspNetCore.Antiforgery.xxxxxxxxxxxxxxxxxxxxxWBCsC7x5LrYIFTqa3CGRihNU-FLOYGFkHBDQ8W-m36dUubxUZj-xxxxxxxxxxxxxxxxxxxxxxGNgpUY; Language=tr
Host: dxxxxxxxxxxxxxxxxxxxx
Referer: https://xxxxxxxxxx/Home/Service
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/127.0.0.0 Safari/537.36
sec-ch-ua: “Not)A;Brand”;v=”99″, “Brave”;v=”127″, “Chromium”;v=”127″
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: “Windows”
sec-gpc: 1
sec-fetch-site: same-origin
sec-fetch-mode: no-cors
sec-fetch-dest: image
priority: i

–122d0000-F–
HTTP/1.1 500 Internal Server Error

–122d0000-H–
Message: Access denied with code 403 (phase 2). Pattern match “(?:/!?|/|[‘;]–|–[srnvf]|–[^-]?-|[^&-]#.?[srnvf]|;?x00)” at REQUEST_COOKIES:.AspNetCore.Antiforgery.h8nIiv1b7VI. [file “C:

I have developed a website, and I’m experiencing an issue where my client encounters a 403 Access Denied error after being logged into the admin panel for a while. Once this error occurs, they cannot access the admin panel again for a certain period.

The error seems to happen when they are editing some texts on the site. According to the server