Update error-526.mdx

added this part: 

If you are using self-signed SSL certificate at the origin server, use the following workaround to avoid an HTTP Error 526.

Add your self-signed SSL certificate to the Custom Origin Trust Store. This allows the Cloudflare edge to recognize your self-signed SSL certificate as valid.
In your Worker's configuration, enable the cots_on_external_fetch compatibility flag. This flag enables the use of the Custom Origin Trust Store when making external (grey-clouded) subrequests from a Cloudflare Worker.

Author: Kiki-Y123

src/content/docs/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-526.mdx

@@ -39,6 +39,12 @@ Workers subrequests to any hostname outside your Cloudflare zone that is not pro
 
 As a result, a valid SSL certificate is required at the origin server.
 
+If you are using self-signed SSL certificate at the origin server, use the following workaround to avoid an HTTP Error `526`.
+
+1. Add your self-signed SSL certificate to the **[`Custom Origin Trust Store`](/ssl/origin-configuration/custom-origin-trust-store/)**. This allows the Cloudflare edge to recognize your self-signed SSL certificate as valid.
+2. In your Worker's configuration, enable the **[`cots_on_external_fetch` compatibility flag](/workers/configuration/compatibility-flags/#do-not-use-the-custom-origin-trust-store-for-external-subrequests)**. This flag enables the use of the **[`Custom Origin Trust Store`](/ssl/origin-configuration/custom-origin-trust-store/)** when making external (grey-clouded) subrequests from a Cloudflare Worker.
+
+
 ### Resolution
 
 :::note
@@ -56,4 +62,4 @@ Request your server administrator or hosting provider to review the origin web s
 
 ![Screen showing an SSL certificate with no errors.](~/assets/images/support/hc-import-troubleshooting_5xx_errors_sslshopper_output.png)
 
-If the origin server uses a self-signed certificate, configure the domain to use _Full_ _SSL_ instead of _Full SSL (Strict)_. Refer to [recommended SSL settings for your origin](/ssl/origin-configuration/ssl-modes).
+If the origin server uses a self-signed certificate, configure the domain to use _Full_ _SSL_ instead of _Full SSL (Strict)_. Refer to [recommended SSL settings for your origin](/ssl/origin-configuration/ssl-modes).