Referrer policy changed on iframe when plugin is activated

Hi,

Short description :
When WP-Matomo Integration plugin is activated, the HTTP header Referrer policy for a vimeo iframe is changed from “strict-origin-when-cross-origin” to “same-origin”, preventing the Vimeo video to be displayed on the page (with the vimeo specific domain restriction for embedding).

Long description :
Some vimeo embedded videos stopped working on my wordpress website after I installed WP-Matomo Integration. The videos are only allowed to be embed on the website domain (it’s a feature from Vimeo). First, I thought it was coming from Vimeo and contacted their support. We identified the problem was coming from the referrer policy HTTP header for the iframe (used to embed the video) : same-origin whereas Vimeo needs cross-origin.

So the problem was coming from my wordpress instance and I made the link with the recent installation of the plugin WP-Matomo Integration. I did the test immediately, disabled the plugin WP-Matomo Integration, reloaded the page, and the vimeo was embedded again (iframe HTTP header Referrer Policy: strict-origin-when-cross-origin). I re-enabled the plugin, the video could not be displayed (iframe HTTP header Referrer Policy: same-origin).

Weirdly enough, on some other pages, the embedded videos are displayed despite the fact that the plugin is enabled.

I could not find anything relevant in the plugin settings (pretty new to Matomo though) and Matomo tracking seems to be working fine.

Any ideas? A setting I can change?

Thanks!

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