Today I faced an in an existing plugin which was working earlier. During investigation, I found that this is caused by the “HttpUtility.UrlEncode(clientSecret)” as shown in below code snippet image

HTTPUtilitySecurityError

I found 2 ways to fix this issue

  1. User “System.Net.WebUtility.UrlEncode()” instead of “System.Web.HttpUtility.UrlEncode()”.
  2. Use “System.Uri.EscapeDataString() ” instead of “System.Web.HttpUtility.UrlEncode()”. as suggested in the this blog post by Nishant Rana.

Thanks-