fix: Fix backtick and code rendering in links

[basilaiman]

Marked version: 16.3.0

Markdown flavor: CommonMark

Description

Fixes rendering of code spans with backticks inside link text.

• Fixes A backtick in code in a link parses incorrectly #1663

When a link contains a code span with backticks inside. The code span was being tokenized separately from the link, resulting in malformed HTML output.

Example

[`` this is a backtick ` and it breaks stuff ``](https://example.com)

Expectation

<p><a href="https://example.com"><code>this is a backtick ` and it breaks stuff</code></a></p>

Result

<p>[<code>this is a backtick ` and it breaks stuff</code>](<a href="https://example.com">https://example.com</a>)</p>

What was attempted

Updated the _inlineLabel pattern to match the proper code span syntax that handles multiple backticks as delimiters:

`+[^`]*?`+(?!`)

Contributor

• Test(s) exist to ensure functionality and minimize regression (if no tests added, list tests covering this PR); or,
• no tests required for this PR.
• If submitting new feature, it has been documented in the appropriate places.

Committer

In most cases, this should be a different person than the contributor.

• CI is green (no forced merge required).
• Squash and Merge PR following conventional commit guidelines.

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[gemini-code-assist]

Summary of Changes

Hello @basilaiman, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a critical parsing bug in Markdown rendering where code spans containing backticks within link text were not correctly processed, resulting in invalid HTML. By refining the regular expression responsible for identifying inline labels, the change ensures that these complex Markdown structures are accurately interpreted and rendered, significantly improving the robustness and correctness of the Markdown parser. The inclusion of new test cases, particularly for ReDoS vulnerabilities, further strengthens the stability of the parsing logic.

Highlights

• Fix Rendering of Code Spans in Links: This pull request resolves an issue where code spans containing backticks within link text were incorrectly parsed, leading to malformed HTML output. The fix ensures proper rendering of such Markdown constructs.
• Updated _inlineLabel Regular Expression: The core of the fix involves modifying the _inlineLabel regular expression in src/rules.ts. The updated regex now correctly handles code spans that use multiple backticks as delimiters, ensuring they are properly recognized within link labels.
• Added Comprehensive Test Cases: New test files have been introduced to validate the fix and prevent regressions. These include specific tests for links with internal backticks (backticks_in_links.md/.html) and several ReDoS (Regular Expression Denial of Service) test cases (backticks_alternating_in_link.md/.html, backticks_in_link_label.md/.html) to ensure the updated regex is performant and secure.

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[gemini-code-assist]

Code Review

This pull request aims to fix an issue with rendering code spans that contain backticks within link labels. While the intention is correct and new tests have been added to cover this scenario, the regular expression change in src/rules.ts appears to be flawed. It does not correctly handle code spans with backticks inside them, which contradicts the goal of this PR. I've left a specific comment detailing the issue with the regex.

[UziTech]

Thanks! 💯

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Project	Deployment	Preview	Comments	Updated (UTC)
marked-website	Ready	Preview	Comment	Oct 4, 2025 5:21am