gitea: Blank page with "Invalid csrf token."

• Gitea version (or commit ref): 1.13.0
• Git version: 2.25.1
• Operating system: Ubuntu Server 20.04
• Database (use [x]):
  • PostgreSQL
  • MySQL
  • MSSQL
  • SQLite
• Can you reproduce the bug at https://try.gitea.io:
  • Yes (provide example URL)
  • No
  • Haven’t tried
• Log gist: N/A

Description

When clicking buttons or adding comments in issues I often see a blank page saying Invalid csrf token., which I had to work around using a refresh and a re-click, which has problems such as losing text already typed up in the comments. This could be related to me using a lot of tabs.

Issues that this might be related to are:

• #4311: seems very similar, but locked so no discussion can be continued. Don’t quite understand how it is closed as #11182 doesn’t seem to be solution to this page appearing and proposes to log out instead (why though and how does it make things better?).
• #11188: proposes switching to SameSite=strict cookies instead, which seem to be able to fix this issue. Still filling this issue since this is not what a user might expect so should be better categorized as a bug than a proposal. Also, fixing this issue doesn’t directly necessitate using #11188 and other fixes might be possible.