tl;dr: Ensure you are upgraded to at least 6.2.7 and 6.3.1
CVE-2019-9853: Insufficient URL decoding flaw in categorizing macro
LibreOffice documents can contain macros. The execution of those macros
is controlled by the document security settings, typically execution of
macros are blocked by default.
A URL decoding flaw existed in how the urls to the macros within the
document were processed and categorized, resulting in the possibility
to construct a document where macro execution bypassed the security
The documents were correctly detected as containing macros, and
prompted the user to their existence within the documents, but macros
within the document were subsequently not controlled by the security
settings allowing arbitrary macro execution
This issue affects:
LibreOffice 6.2 series versions prior to 6.2.6;
LibreOffice 6.3 series versions prior to 6.3.1.
Because CVE-2019-9854 and CVE-2019-9855 exist in 6.2.6, 6-2 series
users are recommended to upgrade to 6.2.7
Thanks to Nils Emmerich of ERNW Research GmbH for discovering and
reporting this issue.