This update for htmldoc fixes the following issues:

htmldoc was updated to version 1.9.12

* Fixed buffer-overflow CVE-2021-20308 ( boo#1184424 )
* Fixed a crash bug with "data:" URIs and EPUB output
* Fixed several other crash bugs
* Fixed JPEG error handling
* Fixed some minor issues
* Removed the bundled libjpeg, libpng, and zlib.

update to 1.9.11:

- Added high-resolution desktop icons for Linux.
- Updated the internal HTTP library to fix truncation of redirection URLs
- Fixed a regression in the handling of character entities for UTF-8 input
- The `--numbered` option did not work when the table-of-contents was disabled
- Updated local zlib to v1.2.11.
- Updated local libpng to v1.6.37.
- Fixed packaging issues on macOS and Windows
- Now ignore sRGB profile errors in PNG files
- The GUI would crash when saving
- Page comments are now allowed in `pre` text

update to 1.9.9:

- Added support for a `HTMLDOC.filename` META keyword that controls the filename
  reported in CGI mode; the default remains "htmldoc.pdf" (Issue #367)
- Fixed a paragraph formatting issue with large inline images (Issue #369)
- Fixed a buffer underflow issue (Issue #370)
- Fixed PDF page numbers (Issue #371)
- Added support for a new `L` header/footer format (`$LETTERHEAD`), which
  inserts a letterhead image at its full size (Issue #372, Issue #373,
  Issue #375)
- Updated the build documentation (Issue #374)
- Refactored the PRE rendering code to work around compiler optimization bugs
- Added support for links with targets (Issue #351)
- Fixed a table rowspan + valign bug (Issue #360)
- Added support for data URIs (Issue #340)
- HTMLDOC no longer includes a PDF table of contents when converting a single
  web page (Issue #344)
- Updated the markdown support with external links, additional inline markup,
  and hard line breaks.
- Links in markdown text no longer render with a leading space as part of the
  link (Issue #346)
- Fixed a buffer underflow bug discovered by AddressSanitizer.
- Fixed a bug in UTF-8 support (Issue #348)
- PDF output now includes the base language of the input document(s)
- Optimized the loading of font widths (Issue #354)
- Optimized PDF page resources (Issue #356)
- Optimized the base memory used for font widths (Issue #357)
- Added proper `­` support (Issue #361)
- Title files can now be markdown.
- The GUI did not support EPUB output.
- Empty markdown table cells were not rendered in PDF or PostScript output.
- The automatically-generated title page now supports both "docnumber" and
  "version" metadata.
- Added support for dc:subject and dc:language metadata in EPUB output from the
  HTML keywords and lang values.
- Added support for the subject and language metadata in markdown input.
- Fixed a buffer underflow bug (Issue #338)
- `htmldoc --help` now reports whether HTTPS URLs are supported (Issue #339)
- Fixed an issue with HTML title pages and EPUB output.
- Inline fixed-width text is no longer reduced in size automatically
- Optimized initialization of font width data (Issue #334)
- Fixed formatting bugs with aligned images (Issue #322, Issue #324)
- Fixed support for three digit "#RGB" color values (Issue #323)
- Fixed character set support for markdown metadata.
- Updated libpng to v1.6.34 (Issue #326)
- The makefiles did not use the CPPFLAGS value (Issue #328)
- Added Markdown table support.
- Fixed parsing of TBODY, TFOOT, and THEAD elements in HTML files.