1833581 - Videos can not be played at threadreaderapp.com with ETP set to STRICT

Status: NEW

(Core :: Privacy: Anti-Tracking, defect, P3)

Description

[Raul Bucata]

Attachment: testeststse.png

Environment:
Operating System: Windows 10 PRO x64
Firefox version: Firefox Nightly 115.0a1 (2023-05-16) (64-bit)

Preconditions:
ETP set to STRICT/STANDARD
Clean profile

Steps to reproduce:

1. Navigate to: https://threadreaderapp.com/thread/1657755496852475906.html
2. Locate a video placeholder by scrolling the page.
3. Observe the result.

Expected Behavior:
Videos can be viewed and played from the placeholders.

Actual Behavior:
"No video with supported format and mime type found" error is displayed inside the video placeholders.

Notes:

• Not reproducible with ETP STANDARD/STRICT.
• Might be related to: https://bugzilla.mozilla.org/show_bug.cgi?id=1753590
• Reproducible in PRIVATE Mode as well.
• Screenshot is attached.