Issue tag v20.18.

Changelog.md

@@ -3,6 +3,11 @@ means week 46 of year 2013. Should a second tag be given the same week, an index
 
 Starting from v18.47, the ticket numbers in bold are those that might break compatibility in models.
 
+# v20.18
+
+_An improvement of #1506 that arrived just after the release of v20.17:_
+
+- Improve the QuasiIncompressibleSecondPiolaKirchhoffStressTensor operator so that we do not have permission issues in CardiacMechanics model.
 
 # v20.17