Prepare for 2.10.0 release

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: colinodell

CHANGELOG.md

@@ -6,6 +6,10 @@ Updates should follow the [Keep a CHANGELOG](https://keepachangelog.com/) princi
 
 ## [Unreleased][unreleased]
 
+## [2.10.0] - 2026-08-11
+
+This is a **security release** to address a denial of service vulnerability in the `AttributesExtension`.
+
 ### Added
 - Added a new `table_of_contents/max_placeholder_entries` option to limit how many table of contents entries a document may render across all of its placeholders (#1134)
 - Added `Cursor::matchInPlace()`, which matches a regular expression at the cursor's position within the line using PCRE's native offset semantics instead of copying the remainder (#1145)
@@ -830,7 +834,8 @@ No changes were introduced since the previous release.
     - Alternative 1: Use `CommonMarkConverter` or `GithubFlavoredMarkdownConverter` if you don't need to customize the environment
     - Alternative 2: Instantiate a new `Environment` and add the necessary extensions yourself
 
-[unreleased]: https://github.com/thephpleague/commonmark/compare/2.9.2...HEAD
+[unreleased]: https://github.com/thephpleague/commonmark/compare/2.10.0...HEAD
+[2.10.0]: https://github.com/thephpleague/commonmark/compare/2.9.2...2.10.0
 [2.9.2]: https://github.com/thephpleague/commonmark/compare/2.9.1...2.9.2
 [2.9.1]: https://github.com/thephpleague/commonmark/compare/2.9.0...2.9.1
 [2.9.0]: https://github.com/thephpleague/commonmark/compare/2.8.3...2.9.0

composer.json

@@ -116,7 +116,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-main": "2.10-dev"
+            "dev-main": "2.11-dev"
         }
     },
     "config": {

docs/2.x/security.md

@@ -128,6 +128,14 @@ The `xml/max_indentation_level` option (default: `16`) caps how far elements are
 
 Note that `max_nesting_level` is *not* sufficient on its own here, as it only constrains how deeply **blocks** may nest - deeply-nested inlines (like `_______...`) can still produce a deep tree.
 
+## Table of Contents Placeholders
+
+This only applies if you're using the [Table of Contents extension](/2.x/extensions/table-of-contents/) with `'position' => 'placeholder'`.
+
+In placeholder mode every placeholder renders its own copy of the table of contents, so a document containing many headings *and* many placeholders repeats that whole list at each one.  A small input can therefore produce output many times its size.
+
+The `table_of_contents/max_placeholder_entries` option bounds the total number of entries rendered across all of a document's placeholders; any placeholder beyond that budget is left as-is.  It defaults to `null` (no limit) for backward compatibility, so setting an `int` is recommended when rendering untrusted input.
+
 ## Additional Filtering
 
 Although this library does offer these security features out-of-the-box, some users may opt to also run the HTML output through additional filtering layers (like HTMLPurifier).  If you do this, make sure you **thoroughly** test your additional post-processing steps and configure them to work properly with the types of HTML elements and attributes that converted Markdown might produce, otherwise, you may end up with weird behavior like missing images, broken links, mismatched HTML tags, etc.

docs/2.x/upgrading.md

@@ -16,6 +16,64 @@ redirect_from:
 
 # Upgrading to Newer Versions
 
+## Upgrading from 2.9 to 2.10
+
+There are no breaking API changes when upgrading from 2.9 to 2.10, but two constants were deprecated and a few
+behaviors changed for integrations which hook into the affected extensions.
+
+### The Table of Contents Is Rendered Once Per Document
+
+In `placeholder` mode the table of contents is now rendered a single time and that one result is shared across every
+placeholder, instead of the whole subtree being cloned into each of them.  A custom renderer registered for the
+`TableOfContents` node is therefore no longer called once per placeholder, and must return the same markup each time it
+is called for a given document.  The first placeholder still receives the `TableOfContents` node itself, so listeners
+which locate and reposition that node continue to work.
+
+### Recommended: Bound Table of Contents Placeholders
+
+Every placeholder legitimately renders its own copy of the table of contents, so a document with many headings and many
+placeholders can produce output far larger than its input.  If you're parsing untrusted input in `placeholder` mode, we
+now recommend setting the new `table_of_contents/max_placeholder_entries` option, which bounds the total number of
+entries rendered across all of a document's placeholders; placeholders beyond that budget are left as-is.  It defaults
+to `null` (unlimited) for backward compatibility.
+
+### `default_attributes` Accepts a New Configuration Shape
+
+`default_attributes` still accepts the node attribute map on its own, and now also accepts that map paired with a new
+`strict_callables` option:
+
+```php
+$config = [
+    'default_attributes' => [
+        'attributes' => [Paragraph::class => ['class' => 'text']],
+        'strict_callables' => true,
+    ],
+];
+```
+
+With `strict_callables` enabled only closures and invokable objects are treated as callbacks, so strings and arrays are
+always used as literal attribute values.  This keeps a value which happens to share its name with a PHP function - such
+as `'class' => 'link'`, `'header'`, `'key'`, `'range'`, or `'current'` - from being invoked instead of used.  A callback
+written as a string or array callable can be wrapped with `Closure::fromCallable()`.
+
+Reading the option back has changed shape to match: `$environment->getConfiguration()->get('default_attributes')` now
+returns the normalized structure, so read `default_attributes/attributes` to get the node map.  The `strict_callables`
+option is itself deprecated, and will be removed in 3.0 when only closures and invokable objects will ever be treated
+as callbacks.
+
+### Custom Unique Slug Normalizers Are No Longer Wrapped
+
+A custom `UniqueSlugNormalizerInterface` implementation is now used directly rather than being wrapped by the built-in
+`UniqueSlugNormalizer`.  Such implementations now receive the `clearHistory()` calls the interface documents - without
+which slug history leaked between documents when `slug_normalizer/unique` was set to `'document'` - and are trusted to
+enforce uniqueness themselves, so the extra deduplication the wrapper applied on top of them is no longer performed.
+
+### Deprecated: Anchored `RegexHelper` Constants
+
+`RegexHelper::PARTIAL_LINK_TITLE` and `RegexHelper::REGEX_LINK_DESTINATION_BRACES` are deprecated.  Use the new
+unanchored `RegexHelper::PARTIAL_LINK_TITLE_UNANCHORED` and `RegexHelper::PARTIAL_LINK_DESTINATION_BRACES` fragments
+with an anchor of your own choosing instead.
+
 ## Upgrading from 2.8 to 2.9
 
 There are no breaking API changes when upgrading from 2.8 to 2.9, but several security fixes change the output of