Hello, I have a problem with YouTube videos not playing on any website when using Mozilla Firefox. Whenever a site (like zamunda.net or other forums) embeds a YouTube video, I get the following message: “Error 153 – video player configuration error” or sometimes “For your protection, this page will not allow Firefox to display the embedded content. To view this page, you must open it in a new window.” If I open the same video directly on YouTube (youtube.com), it plays fine. This issue happens on all websites that have embedded YouTube videos, not just one. Windows 11 25H2 Firefox Last Version Could this be related to codec support (H.264 / MSE) or a security restriction with embedded frames? Any suggestions on how to fix or debug this would be appreciated. Thank you, Panche