CHANGELOG.md

MD4C Change Log

Next Version (Work in Progress)

Fixes:

• #236: Fix quadratic time behavior caused by one-by-one walking over block lines instead of calling md_lookup_line().

• #238: Fix quadratic time and output size behavior caused by malicious misuse of link reference definitions.

Version 0.5.2

Changes:

• Changes mandated by CommonMark specification 0.31:

  • The specification expands set of Unicode characters seen by Markdown parser as a punctuation. Namely all Unicode general categories P (punctuation) and S (symbols) are now seen as such.

  • The definition of HTML comment has been changed so that <!--> and <!---> are also recognized as HTML comments.

  • HTML tags recognized as HTML block starting condition of type 4 has been updated, namely a tag <source> has been removed, whereas <search> added.

  Refer to CommonMark 0.31.2 for full specification.

Fixes:

• #230: The fix #223 in 0.5.1 release was incomplete and one corner case remained unfixed. This is now addressed.

• #231: md2html --full-html now emits <meta charset="UTF-8"> in the HTML header.

Version 0.5.1

Changes:

• LaTeX math extension (MD_FLAG_LATEXMATHSPANS) now requires that opener mark is not immediately preceded with alpha-numeric character and similarly that closer mark is not immediately followed with alpha-numeric character.

  So for example foo$ x + y = z $ is not recognized as LaTeX equation anymore because there is no space between foo and the opening $.

• Table extension (MD_FLAG_TABLES) now recognizes only tables with no more than 128 columns. This limit has been imposed to prevent a pathological case of quadratic output size explosion which could be used as DoS attack vector.

• We are now more strict with MD_FLAG_PERMISSIVExxxAUTOLINKS family of extensions with respect to non-alphanumeric characters, with the aim to mitigate false positive detections.

  Only relatively few selected non-alphanumeric are now allowed in permissive e-mail auto-links (MD_FLAG_PERMISSIVEEMAILAUTOLINKS):

  • ., -, _, + in user name part of e-mail address; and
  • ., -, _ in host part of the e-mail address.

  Similarly for URL and e-mail auto-links (MD_FLAG_PERMISSIVEURLAUTOLINKS and MD_FLAG_PERMISSIVEWWWAUTOLINKS):

  • ., -, _ in host part of the URL;
  • /, ., -, _ in path part of the URL;
  • &, ., -, +, _, =, (, ) in the query part of the URL (additionally, if present, ( and ) must form balanced pairs); and
  • ., -, +, _ in the fragment part of the URL.

  Furthermore these characters (with some exceptions like where they serve as delimiter characters, e.g. / for paths) are generally accepted only when an alphanumeric character both precedes and follows them (i.e. these cannot be "stacked" together).

Fixes:

• Fix several bugs where we haven't properly respected already resolved spans of higher precedence level in handling of permissive auto-links extensions (family of MD_FLAG_PERMISSIVExxxAUTOLINKS flags), LaTeX math extension (MD_FLAG_LATEXMATHSPANS) and wiki-links extension (MD_FLAG_WIKILINKS) of the form [[label|text]] (with pipe |). In some complex cases this could lead to invalid internal parser state and memory corruption.

  Identified with OSS-Fuzz.

• #222: Fix strike-through extension (MD_FLAG_STRIKETHROUGH) which did not respect same rules for pairing opener and closer marks as other emphasis spans.

• #223: Fix incorrect handling of new-line character just at the beginning and/or end of a code span where we were not following CommonMark specification requirements correctly.

Version 0.5.0

Changes:

• Changes mandated by CommonMark specification 0.30.

  Actually there are only very minor changes to recognition of HTML blocks:

  • The tag <textarea> now triggers HTML block (of type 1 as per the specification).

  • HTML declaration (HTML block type 4) is not required to begin with an upper-case ASCII character after the <!. Any ASCII character is now allowed. Also it now doesn't require a whitespace before the closing >.

  Other than that, the newest specification mainly improves test coverage and clarifies its wording in some cases, without affecting the implementation.

  Refer to CommonMark 0.30 for full specification.

• Make Unicode-specific code compliant to Unicode 15.1.

• Update list of entities known to the HTML renderer from https://html.spec.whatwg.org/entities.json.

New Features:

• Add extension allowing to treat all soft break as hard ones. It has to be explicitly enabled with MD_FLAG_HARD_SOFT_BREAKS.

  Contributed by l-m.

• Structure MD_SPAN_A_DETAIL now has a new member is_autolink.

  Contributed by Jens Alfke.

• md2html utility now supports command line options --html-title and --html-css.

  Contributed by Andreas Baumann.

Fixes:

• #163: Make HTML renderer to emit '\n' after the root tag when in the XHTML mode.

• #165: Make HTML renderer not to percent-encode '~' in URLs. Although it does work, it's not needed, and it can actually be confusing with URLs such as http://www.example.com/~johndoe/.

• #167, #168: Fix multiple instances of various buffer overflow bugs, found mostly using a fuzz testing. Contributed by dtldarek and Thierry Coppey.

• #169: Table underline now does not require 3 characters per table column anymore. One dash (optionally with a leading or tailing : appended or prepended) is now sufficient. This improves compatibility with the GFM.

• #172: Fix quadratic time behavior caused by unnecessary lookup for link reference definition even if the potential label contains nested brackets.

• #173, #174, #212, #213: Multiple bugs identified with OSS-Fuzz were fixed.

• #190, #200, #201: Multiple fixes of incorrect interactions of indented code block with a preceding block.

• #202: We were not correctly calling enter_block() and leave_block() callbacks if multiple HTML blocks followed one after another; instead previously such blocks were merged into one.

  (This may likely impact only applications interested in Markdown's AST, and not just converting Markdown to other formats like HTML.)

• #210: The md2html utility now handles nested images with optional titles correctly.

• #214: Tags <h2> ... <h6> incorrectly did not trigger HTML block.

• #215: The parser incorrectly did not accept optional tabs after setext header underline.

• #217: The parser incorrectly resolved emphasis in some situations, if the emphasis marks were enclosed by punctuation characters.

Version 0.4.8

Fixes:

• #149: A HTML block started in a container block (and not explicitly finished in the block) could eat 1 line of actual contents.

• #150: Fix md2html to output proper DOCTYPE and HTML tags when --full-html command line options is used, accordingly to the expected output format (HTML or XHTML).

• #152: Suppress recognition of a permissive autolink if it would otherwise form a complete body of an outer inline link.

• #153, #154: Set MD_BLOCK_UL_DETAIL::mark and MD_BLOCK_OL_DETAIL::mark_delimiter correctly, even when the blocks are nested at the same line in a complicated ways.

• #155: Avoid reading 1 character beyond the input size in some complex cases.

Version 0.4.7

Changes:

• Add MD_TABLE_DETAIL structure into the API. The structure describes column count and row count of the table, and pointer to it is passed into the application-provided block callback with the MD_BLOCK_TABLE block type.

Fixes:

• #131: Fix handling of a reference image nested in a reference link.

• #135: Handle unmatched parenthesis pairs inside a permissive URL and WWW auto-links in a way more compatible with the GFM.

• #138: The tag <tbody></tbody> is now suppressed whenever the table has zero body rows.

• #139: Recognize a list item mark even when EOF follows it.

• #142: Fix reference link definition label matching in a case when the label ends with a Unicode character with non-trivial case folding mapping.

Version 0.4.6

Fixes:

• #130: Fix ISANYOF macro, which could provide unexpected results when encountering zero byte in the input text; in some cases leading to broken internal state of the parser.

  The bug could result in denial of service and possibly also to other security implications. Applications are advised to update to 0.4.6.

Version 0.4.5

Fixes:

• #118: Fix HTML renderer's MD_HTML_FLAG_VERBATIM_ENTITIES flag, exposed in the md2html utility via --fverbatim-entities.

• #124: Fix handling of indentation of 16 or more spaces in the fenced code blocks.

Version 0.4.4

Changes:

• Make Unicode-specific code compliant to Unicode 13.0.

New features:

• The HTML renderer, developed originally as the heart of the md2html utility, is now built as a standalone library, in order to simplify its reuse in applications.

• With MD_HTML_FLAG_SKIP_UTF8_BOM, the HTML renderer now skips UTF-8 byte order mark (BOM) if the input begins with it, before passing to the Markdown parser.

  md2html utility automatically enables the flag (unless it is custom-built with -DMD4C_USE_ASCII).

• With MD_HTML_FLAG_XHTML, The HTML renderer generates XHTML instead of HTML.

  This effectively means <br /> instead of <br>, <hr /> instead of <hr>, and <img ... /> instead of <img ...>.

  md2html utility now understands the command line option -x or --xhtml enabling the XHTML mode.

Fixes:

• #113: Add missing folding info data for the following Unicode characters: U+0184, U+018a, U+01b2, U+01b5, U+01f4, U+0372, U+038f, U+1c84, U+1fb9, U+1fbb, U+1fd9, U+1fdb, U+1fe9, U+1feb, U+1ff9, U+1ffb, U+2c7f, U+2ced, U+a77b, U+a792, U+a7c9.

  Due the bug, the link definition label matching did not work in the case insensitive way for these characters.

Version 0.4.3

New features:

• With MD_FLAG_UNDERLINE, spans enclosed in underscore (_foo_) are seen as underline (MD_SPAN_UNDERLINE) rather than an ordinary emphasis or strong emphasis.

Changes:

• The implementation of wiki-links extension (with MD_FLAG_WIKILINKS) has been simplified.

  • A noticeable increase of MD4C's memory footprint introduced by the extension implementation in 0.4.0 has been removed.
  • The priority handling towards other inline elements have been unified. (This affects an obscure case where syntax of an image was in place of wiki-link destination made the wiki-link invalid. Now all inline spans in the wiki-link destination, including the images, is suppressed.)
  • The length limitation of 100 characters now always applies to wiki-link destination.

• Recognition of strike-through spans (with the flag MD_FLAG_STRIKETHROUGH) has become much stricter and, arguably, reasonable.

  • Only single tildes (~) and double tildes (~~) are recognized as strike-through marks. Longer ones are not anymore.
  • The length of the opener and closer marks have to be the same.
  • The tildes cannot open a strike-through span if a whitespace follows.
  • The tildes cannot close a strike-through span if a whitespace precedes.

  This change follows the changes of behavior in cmark-gfm some time ago, so it is also beneficial from compatibility point of view.

• When building MD4C by hand instead of using its CMake-based build, the UTF-8 support was by default disabled, unless explicitly asked for by defining a preprocessor macro MD4C_USE_UTF8.

  This has been changed and the UTF-8 mode now becomes the default, no matter how md4c.c is compiled. If you need to disable it and use the ASCII-only mode, you have explicitly define macro MD4C_USE_ASCII when compiling it.

  (The CMake-based build as provided in our repository explicitly asked for the UTF-8 support with -DMD4C_USE_UTF8. I.e. if you are using MD4C library built with our vanilla CMakeLists.txt files, this change should not affect you.)

Fixes:

• Fixed some string length handling in the special MD4C_USE_UTF16 build.

  (This does not affect you unless you are on Windows and explicitly define the macro when building MD4C.)

• #100: Fixed an off-by-one error in the maximal length limit of some segments of e-mail addresses used in autolinks.

• #107: Fix mis-detection of asterisk-encoded emphasis in some corner cases when length of the opener and closer differs, as in ***foo *bar baz***.

Version 0.4.2

Fixes:

• #98: Fix mis-detection of asterisk-encoded emphasis in some corner cases when length of the opener and closer differs, as in **a *b c** d*.

Version 0.4.1

Unfortunately, 0.4.0 has been released with badly updated ChangeLog. Fixing this is the only change on 0.4.1.

Version 0.4.0

New features:

• With MD_FLAG_LATEXMATHSPANS, LaTeX math spans ($...$) and LaTeX display math spans ($$...$$) are now recognized. (Note though that the HTML renderer outputs them verbatim in a custom <x-equation> tag.)

  Contributed by Tilman Roeder.

• With MD_FLAG_WIKILINKS, Wiki-style links ([[...]]) are now recognized. (Note though that the HTML renderer renders them as a custom <x-wikilink> tag.)

  Contributed by Nils Blomqvist.

Changes:

• Parsing of tables (with MD_FLAG_TABLES) is now closer to the way how cmark-gfm parses tables as we do not require every row of the table to contain a pipe | anymore.

  As a consequence, paragraphs now cannot interrupt tables. A paragraph which follows the table has to be delimited with a blank line.

Fixes:

• #94: md_build_ref_def_hashtable(): Do not allocate more memory than strictly needed.

• #95: md_is_container_mark(): Ordered list mark requires at least one digit.

• #96: Some fixes for link label comparison.

Version 0.3.4

Changes:

• Make Unicode-specific code compliant to Unicode 12.1.

• Structure MD_BLOCK_CODE_DETAIL got new member fenced_char. Application can use it to detect character used to form the block fences (` or ~). In the case of indented code block, it is set to zero.

Fixes:

• #77: Fix maximal count of digits for numerical character references, as requested by CommonMark specification 0.29.

• #78: Fix link reference definition label matching for Unicode characters where the folding mapping leads to multiple codepoints, as e.g. in ẞ -> SS.

• #83: Fix recognition of an empty blockquote which interrupts a paragraph.

Version 0.3.3

Changes:

• Make permissive URL autolink and permissive WWW autolink extensions stricter.

  This brings the behavior closer to GFM and mitigates risk of false positives. In particular, the domain has to contain at least one dot and parenthesis can be part of the link destination only if ( and ) are balanced.

Fixes:

• #73: Some raw HTML inputs could lead to quadratic parsing times.

• #74: Fix input leading to a crash. Found by fuzzing.

• #76: Fix handling of parenthesis in some corner cases of permissive URL autolink and permissive WWW autolink extensions.

Version 0.3.2

Changes:

• Changes mandated by CommonMark specification 0.29.

  Most importantly, the white-space trimming rules for code spans have changed. At most one space/newline is trimmed from beginning/end of the code span (if the code span contains some non-space contents, and if it begins and ends with space at the same time). In all other cases the spaces in the code span are now left intact.

  Other changes in behavior are in corner cases only. Refer to CommonMark 0.29 notes for more info.

Fixes:

• #68: Some specific HTML blocks were not recognized when EOF follows without any end-of-line character.

• #69: Strike-through span not working correctly when its opener mark is directly followed by other opener mark; or when other closer mark directly precedes its closer mark.

Version 0.3.1

Fixes:

• #58, #59, #60, #63, #66: Some inputs could lead to quadratic parsing times. Thanks to Anders Kaseorg for finding all those issues.

• #61: Flag MD_FLAG_NOHTMLSPANS erroneously affected also recognition of CommonMark autolinks.

Version 0.3.0

New features:

• Add extension for GitHub-style task lists:

   * [x] foo
   * [x] bar
   * [ ] baz
  

  (It has to be explicitly enabled with MD_FLAG_TASKLISTS.)

• Added support for building as a shared library. On non-Windows platforms, this is now default behavior; on Windows static library is still the default. The CMake option BUILD_SHARED_LIBS can be used to request one or the other explicitly.

  Contributed by Lisandro Damián Nicanor Pérez Meyer.

• Renamed structure MD_RENDERER to MD_PARSER and refactorize its contents a little bit. Note this is source-level incompatible and initialization code in apps may need to be updated.

  The aim of the change is to be more friendly for long-term ABI compatibility we shall maintain, starting with this release.

• Added CHANGELOG.md (this file).

• Make sure md_process_table_row() reports the same count of table cells for all table rows, no matter how broken the input is. The cell count is derived from table underline line. Bogus cells in other rows are silently ignored. Missing cells in other rows are reported as empty ones.

Fixes:

• CID 1475544: Calling md_free_attribute() on uninitialized data.

• #47: Using bad offsets in md_is_entity_str(), in some cases leading to buffer overflow.

• #51: Segfault in md_process_table_cell().

• #53: With MD_FLAG_PERMISSIVEURLAUTOLINKS or MD_FLAG_PERMISSIVEWWWAUTOLINKS we could generate bad output for ordinary Markdown links, if a non-space character immediately follows like e.g. in [link](http://github.com)X.

Version 0.2.7

This was the last version before the changelog has been added.