Intermittent, rare 403 errors from Cloudflare

Website, Application, Performance
22

Sorry for the long delay, but I wanted to report that we were ultimately able to track this 403 down to our AWS WAF rules, specifically this one:

AWSWAFSecurityAutomationsSqlInjectionRule

To anyone else reading this, I can suggest a few things to help you prove to yourself that Cloudflare is not the source of the problem:

  1. verify that the “403 Forbidden” output in the response body is black and white (if it comes from Cloudflare, you will see fancy branding and formatting).
  2. Go into your Cloudfare settings, and in the right column under “Quick Actions”, enable “Development Mode” (which will remporarily bypass the cache)
  3. Farther down, click “Pause Cloudflare on Site”.

Give it a few minutes to take, and then after that the true source of the 403 error will be revealed in the response headers. For me, I started seeing this (instead of “server: Cloudflare”:
image

From there, the problem was cut in half, because we were able to remove Cloudflare completely as a culprit.

At any rate, big thanks to @cloonan and @WhiteDemonhia for helping to troubleshoot.

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