Title: Content Manipulation with Certificate Validation Attack
Announced: October 11, 2021
Fixed in: LibreOffice 7.0.5/7.1.1
LibreOffice supports digital signatures of ODF documents and macros within documents, presenting visual aids that no alteration of the document occurred since the last signing and that the signature is valid.
An Improper Certificate Validation vulnerability in LibreOffice allowed an attacker to self sign an ODF document, with a signature untrusted by the target, then modify it to change the signature algorithm to an invalid (or unknown to LibreOffice) algorithm and LibreOffice would incorrectly present such a signature with an unknown algorithm as a valid signature issued by a trusted person.
Thanks to NDS of Ruhr University Bochum for discovering and reporting this problem.