Title: CVE-2020-12803 XForms submissions could overwrite local files
Announced: June 09, 2020
Fixed in: LibreOffice 6.4.4
ODF documents can contain forms to be filled out by the user. Similar to HTML forms, the contained form data can be submitted to a URI, for example, to an external web server. To create submittable forms, ODF implements the XForms W3C standard, which allows data to be submitted without the need for macros or other active scripting
Prior to version 6.4.4 LibreOffice allowed forms to be submitted to any URI, including file: URIs, enabling form submissions to overwrite local files. User-interaction is required to submit the form, but to avoid the possibility of malicious documents engineered to maximize the possibility of inadvertent user submission this feature has now been limited to http[s] URIs, removing the possibility to overwrite local files.
All users are recommended to upgrade to LibreOffice >= 6.4.4
Thanks to Jens Müller of Ruhr University Bochum for discovering and reporting this problem