Update SECURITY.md

Author: jeffpaul

SECURITY.md

@@ -34,7 +34,7 @@ Once an issue is reported, 10up uses the following disclosure process:
 - When a report is received, we confirm the issue and determine its severity.
 - If we know of specific third-party services or software that require mitigation before publication, those projects will be notified.
 - An advisory is prepared (but not published) which details the problem and steps for mitigation.
-- Wherever possible, fixes are prepared for the last minor release of the two latest major releases, as well as the master branch.  We will attempt to commit these fixes as soon as possible, and as close together as possible.
+- Wherever possible, fixes are prepared for the last minor release of the two latest major releases, as well as the trunk branch.  We will attempt to commit these fixes as soon as possible, and as close together as possible.
 - Patch releases are published for all fixed released versions and the advisory is published.
 - Release notes and our CHANGELOG.md will include a `Security` section with a link to the advisory.