Update changelog text

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
diff --git a/ChangeLog.d/padding-ct-changelog.txt b/ChangeLog.d/padding-ct-changelog.txt
index f89f479..e3d3424 100644
--- a/ChangeLog.d/padding-ct-changelog.txt
+++ b/ChangeLog.d/padding-ct-changelog.txt
@@ -1,6 +1,6 @@
 Security
-   * Fix non-constant-time behaviour in padding calculations in CBC
-     decryption, NIST SP 800-38F key wrapping, and RSAAES-OAEP decryption.
-     For CBC and RSAAES-OAEP, this may have been exploitable in a
-     padding oracle for a privileged local attacker with the ability to
-     observe memory access timings.
+   * Improve padding calculations in CBC decryption, NIST key unwrapping and
+     RSA OAEP decryption. With the previous implementation, some compilers
+     (notably recent versions of Clang) could produce non-constant time code,
+     which could allow a padding oracle attack if the attacker has access to
+     precise timing measurements.