BIT-LIBPYTHON-2026-4786 Incomplete mitigation of CVE-2026-4519, %action expansion for command injection to webbrowser.open()

Mitgation of CVE-2026-4519 was incomplete. If the URL contained "%action" the mitigation could be bypassed for certain browser types the "webbrowser.open" API could have commands injected into the underlying shell. See CVE-2026-4519 for details...