REL: 6.21.4

## What's new

### Security (SEC)
- Limit the number of copied page attributes during flattening (#4290) by @stefan6419846
- Detect EOF when reading standard xref table trailer (#4289) by @stefan6419846
- Fix loop detection when cloning DictionaryObject (#4288) by @stefan6419846

### Documentation (DOC)
- Exclude performance issues from security reports (#4280) by @stefan6419846

[Full Changelog](6.21.3...6.21.4)

Author: stefan6419846

CHANGELOG.md

@@ -1,5 +1,17 @@
 # CHANGELOG
 
+## Version 6.21.4, 2026-10-28
+
+### Security (SEC)
+- Limit the number of copied page attributes during flattening (#4290)
+- Detect EOF when reading standard xref table trailer (#4289)
+- Fix loop detection when cloning DictionaryObject (#4288)
+
+### Documentation (DOC)
+- Exclude performance issues from security reports (#4280)
+
+[Full Changelog](https://github.com/py-pdf/pypdf/compare/6.21.3...6.21.4)
+
 ## Version 6.21.3, 2026-10-27
 
 ### Security (SEC)

pypdf/_version.py

@@ -1 +1 @@
-__version__ = "6.21.3"
+__version__ = "6.21.4"