After Nextcloud 17 Update, I can't sync my linux client with nextcloud

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Nextcloud version: 17
Operating system and version Centos 7.6:
Apache: 2
PHP version: 7

The issue you are facing:

Is this the first time you’ve seen this error?: Y

Steps to replicate it:

  1. Upgrade from 16.04 to 17
  2. Open your Linux nextcloud sync program
  3. Login with your nextcloud address and credentials
  4. The default browser will be open, click on Login
  5. Click on Grant Access
  6. Nothing happens
  7. You will see this error on the browser console (Tried on FF, Chrome, Midori, Opera): Refused to send form data to ‘’ because it violates the following Content Security Policy directive: “form-action ‘self’”.

The output of your Nextcloud log in Admin > Logging:

No errors

The output of your config.php file in /path/to/nextcloud (make sure you remove any identifiable information!):

Default config

Same here!
Also applies to mac clients - However, seems not to be an issue with Android Client

Nextcloud is running behind haproxy reverse proxy
request goes to the nextcloud URL with ssl - but at first (before disabling the plugin) went to collabora URL (dont know why) with the same error mentioned above.

When logging in via Web interface it does not stop loading and does not forward to the user area. Refreshing the page will result in opening the regular user area for logged in users without opening another login prompt.

It’s a problem with the latest Windows client as well. You may want to try using a previous version. There are also the daily builds located here.