Hyperlinks in PDF's navigate top window

If a PDF is shown in an IRFAME and the user clicks on a link (URI Action) inside of this PDF, the link is not opened inside of the IFRAME, but "breaks out" and replaces the content of the top window.

Tested with Edge 91.0.864.64 on Windows 8.1 and Windows 10 (20H2).

This behavior is different to the behavior of Internet Explorer (with Acrobat Reader). In Internet Explorer, the navigation is always inside of the IFRAME.

Due to the new behavior (replacing the content of the top window) the outer web application is unloaded and the user may also lose the session.

Somes additional findings so far:
- it seems to happen only if the PDF was loaded from the same site (domain)
- it happens also, if <EMBED> or "<OBJECT"> is used to embed PDF documents

Other browsers:

- Firefox 89.0.2: Behaves differently: On a computer with Windows 8.1 it navigates inside of the iframe, on a computer with Windows 10 (20H2) it navigates to "top"

- Chrome 91.0.4472.124: navigates to "top" (see https://bugs.chromium.org/p/chromium/issues/detail?id=1040149)