Title: Denylist of executable filename extensions possible to bypass under windows
Announced: April 15, 2021
Fixed in: LibreOffice 7.0.5/7.1.2
LibreOffice has a feature where hyperlinks in a document can be activated by CTRL+click. Under Windows the link can be passed to the system ShellExecute function for handling. LibreOffice contains a denylist of extensions that it blocks from passing to ShellExecute to avoid attempting to launch executables.
In the LibreOffice 7-1 series in versions prior to 7.1.2, and in the 7-0 series in versions prior to 7.0.5, the denylist can be circumvented by manipulating the link so it doesn't match the denylist but results in ShellExecute attempting to launch an executable type.
In the fixed versions this circumvention has been blocked. All Windows users are recommended to upgrade to LibreOffice >= 7.0.5 or >= 7.1.2
Thanks to Lukas Euler of Positive Security for discovering and reporting this problem