Ext+container links broken in Firefox 128.0 64-bit Windows

[atensoftware]

After updating to Firefox 128.0, clicking an ext+container:name=container&url=https://sample.com link opens a blank window in the same container. The extension is grayed out in the Extensions panel, and it is Enabled in the Manage Extensions window.
Instead, ext+container: links should open the URL in the specified container like they did before the update, and the extension should not be grayed out in the Extensions panel.

[DonkeyDoLittle]

Confirming same issue, Firefox 128.0.2, Windows 10 22H2, build 19045.4651

[atensoftware]

Additional information and temporary workaround:

• Issue persists in Firefox 128.0.3, Windows 10, 64-bit
• There is no ext+container registry key in HKEY_CLASSES_ROOT (not sure if this is needed)
• about:config entry for "network.protocol-handler.external.ext+container" exists and is set to "true"
• external container links WORK AS EXPECTED when they are in the Bookmarks Toolbar
• external container links do NOT work when they are in the content of a web page. They open a blank page with the ext+container URL in the address bar. WORKAROUND: Clicking in the address bar and pressing Enter reloads the tab in the correct container and loads the page.

It looks like configuration or security issue, not an issue with the extension itself.

[atensoftware]

I have narrowed down the reproduce steps further.

The above described issue only affects "ext+container" hyperlinks (HTML anchor tags) with the target="_blank" attribute.

Once I removed the attribute, the "ext+container" link worked as expected. I can Ctrl+Click the link to open the URL in a new tab in the correct container.