LibreOffice has a 'stealth mode' in which only documents from locations deemed 'trusted' are allowed to retrieve remote resources.
This mode is not the default mode, but can be enabled by users who want to disable LibreOffice's ability to include remote resources within a document.
A flaw existed where bullet graphics were omitted from this protection prior to version 6.2.5.
HTML Tag | HTML Attribute | Triggers When Opened | Triggers On Save/Export |
---|---|---|---|
ol | src | No | Yes |
ul | src | No | Yes |
The vendor's disclosure for this vulnerability can be found here.
More details and the exploitation process (plus other HTML tag-attribute combination that result in SSRF) can be found in this PDF.