5.2.1

• Add more border width to codemirror cursor (#2983).
• Fix nbconvert handler (#2981).
• Fix the prompt_area argument of the output area constructor (#2961).
• Handle a compound extension in new_untitled (#2949).
• Allow disabling offline message buffering (#2916).

Thanks to the following contributors:

• Steven Silvester (blink1073)
• Grant Nestor (gnestor)
• Jason Grout (jasongrout)
• Min RK (minrk)
• M Pacer (mpacer)

See the 5.2.1 milestone on GitHub for a complete list of pull requests involved in this release.