clipboard operations not working

[jficz]

Steps to reproduce

A) select text in editor

B) select text, press ctrl+c

C1) have a text in clipboard ready
C2) press middle mouse button

D1) have a text in clipboard ready
D2) press ctrl-v

Expected behaviour

A) selected text should appear in clipboard B) selected text should appear in clipboard C) text from clipboard should be pasted to editor D) text from clipboard should be pasted to editor

Actual behaviour

A+B) clipboard contains a strange UTF symbol (
U+2028 I think, I can't paste it anywhere to test except terminal where it says literally '<2028>') C) nothing happens D) works as expected

Server configuration

Operating system: Linux

Web server: Nginx

Database: Percona

PHP version: 7.0

Nextcloud version: 13.0.0

Where did you install Nextcloud from: NextCloud stable channel (zip)

List of activated apps: Is this relevant?

Nextcloud configuration: Is this relevant?

Client configuration

Browser: Firefox 59 and Chromium 65

Operating system: Arch Linux

Logs

Nothing relevant in logs.

Additional info:

I have installed the Markdown extension but the behaviour is the same whether the extension is enabled or not.