HTML::FormHandler versions before 0.410002 for Perl render field attributes into HTML without escaping using the process_attrs method. Any application with fields or field labels where some attributes are built from data rather than literals allows attacker-influenced text in an attribute value that can override the field attributes or embed JavaScript in rendered pages. For example, the RadioGroup widget uses the process_attrs method via the render_option and wrap_radio methods.
https://metacpan.org/release/ABRAXXA/HTML-FormHandler-0.410002/changes
https://github.com/gshank/html-formhandler/commit/a887271e91d755e6486a9f433ae932deb1d2c4a6.patch