Automattic/Jetpack — pull request #23 by kraftbj (2013-12-20 04:37:47+00:00)
Title: Modifies the Image Widget to allow basic HTML in the caption.

WP 3.6 added ability to use HTML in captions. Commit enables this in the widget.
Output is mimics the text widget output method. wp_kses on save using custom list.

Allowed HTML: a[href, title], b, em, i, p, strong