Infinite Scrolling Requests After Topic Deletion

[TethysPlex]

Overview

When a user is actively viewing a topic that is subsequently deleted, continuous scrolling (up or down) triggers an infinite loop of posts.json API calls. These calls consistently return a 403 Forbidden error, yet the application fails to acknowledge the deletion or stop attempting to load non-existent content, leading to persistent background network activity and a broken user experience.

Steps to Reproduce

1. Preparation (Admin/Moderator User):

• Log in as a user with topic deletion privileges (e.g., Administrator or Moderator).
• Create a new topic with a few posts to ensure there’s content to scroll through.
• Keep this topic’s page URL handy.

2. User Experience (Regular User):

• Log in as a regular user (without deletion privileges).
• Open a new browser tab or window.
• Navigate to the topic created in Step 1.
• Open your browser’s developer tools and go to the “Network” tab. Clear any existing requests for a clean view.

3. Simultaneous Deletion & Interaction:

• While the regular user is on the topic page (from Step 2), use the Administrator/Moderator account (from Step 1) to delete the topic.
• Immediately after the topic is deleted, the regular user attempts to scroll up or down on the now-deleted topic’s page.

4. Observe:

• In the regular user’s browser’s Network tab, observe continuous GET requests being sent to https://discourse-url/t/xxxxx/posts.json? (where xxxxx is the deleted topic ID).
• Notice that all these requests consistently return a 403 Forbidden HTTP status code.
• The application does not display any message indicating the topic has been deleted, nor does it stop sending these failed scroll requests.

Potential Consequences

• In my community, we use Cloudflare to prevent cyberattacks, and this bug caused some users to make too many requests and be rate-limited.

[Moin]

What is your current Discourse version?

There was a similar bug report recently which was fixed

A loading loop will occur when user try to fetch the former/latter page of a removed topic

https://github.com/discourse/discourse/pull/35409 For these steps: Login as a user, and read a topic; The admin/moderator removes the topic; Go up/down and trigger the fetch of the former/latter page. Then the page will stuck in an infinite loading, with the console showing 403 forbidden getting /t/${this.topic.id}/posts.json. And if the website is protected by a waf, then the user will be banned from visiting it.