InvalidAuthenticityToken error

Summary

While creating a public issue, a 422 error is returned to the user. After a few attempts to create the problem, I was finally able to capture this error ActionController::InvalidAuthenticityToken

Steps to reproduce

1. Navigate to the snippets page
2. Create a new public snippet

What is the current bug behavior?

Creating a snippet will return a 422 error.

Relevant logs and/or screenshots

[gitlab-unicorn-5f5c55df74-smcx2 unicorn] {"method":"POST","path":"/snippets","format":"html","controller":"SnippetsController","action":"create","status":422,"error":"ActionController::InvalidAuthenticityToken: ActionController::InvalidAuthenticityToken","duration":15.49,"view":0.0,"db":0.0,"time":"2018-11-06T01:44:47.336Z","params":[{"key":"utf8","value":"✓"},{"key":"authenticity_token","value":"[FILTERED]"},{"key":"personal_snippet","value":{"title":"ArrayExamples","description":"Store handy java array examples!","visibility_level":"20","file_name":"ArrayExamples.java","content":"[FILTERED]"}}],"remote_ip":"172.30.151.133","user_id":null,"username":null,"ua":"Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_5) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/11.1.1 Safari/605.1.15"}

GitLab environment info

Expand for output related to GitLab environment info

- Gitlab Version 11.3
- Chart: latest
- Platform:
    - Self-hosted
- Kubernetes: (`kubectl version`)
    - Client:1.10
    - Server:1.11
- Helm: (`helm version`)
    - Client:2.8.2
    - Server:2.8.2