From the Release Notes:
This is a security and bug-fix update.
- Fixed an issue where saving a webpage to disk would sometimes drop tags from the document.
- Fixed an issue with click-to-play plugin content throwing up a blank notification.
- Fixed an issue in the renderer where region intersections would sometimes return the wrong result.
This fixes a regression caused by the fix for CVE-2016-5252.
- Fixed security issues: CVE-2019-11744, CVE-2019-11752, CVE-2019-11737, CVE-2019-11746, CVE-2019-11750, CVE-2019-11747 and CVE-2019-11738.
- Unified XUL Platform Mozilla Security Patch Summary: 7 fixed, 1 DiD, 1 already covered, 22 not applicable.
Update: To get the update now, select "Help" from the Pale Moon menu at the upper left of the browser window. Click About Pale Moon and Check for Updates.