5.5.13 is a maintenance release that rolls up 4 bugfixes for iText 5 Core from the past 5 months:
As of this release XFA Worker is no longer supported on .NET 2.0 - instead you need to use .NET 4.0.
Support has been added for License Key Library 3.0.1. Users on License Key Library 1.0.x should migrate to 3.0.1.
3 bugfixes for iText 5 Core
1 bugfix for XFA Worker
5.5.13 (commercial add-on, not on GitHub).
Please be informed that at the same time we release pdfXFA 1.0.3, an add-on for iText 7. All bugfixes for XFA Worker 5.5.13 were ported to pdfXFA 1.0.3.
No new functionality has been added since 5.5.11.
Still questions about the release, don't hesitate to contact us.