Potential fix for code scanning alert no. 18: Bad HTML filtering regexp#167
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Summary of ChangesHello @BaseMax, 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 code scanning alert by enhancing the HTML minification process. It specifically refines the regular expressions responsible for processing <script> and <style> tags within the Highlights
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Code Review
This pull request aims to fix a security vulnerability related to insecure regular expressions for HTML filtering. The changes correctly make the regex for <script> and <style> tags case-insensitive and allow for attributes.
However, the implementation introduces a critical bug. The replacement logic strips all attributes from the matched tags. This will break external scripts that use the src attribute, as they will be replaced with empty <script> tags. A similar issue exists for <style> tags, where attributes like media would be lost.
I've added two review comments with suggestions to fix this by capturing and preserving the original tags and their attributes during minification.
| r"(?is)<script\b[^>]*>(.*?)</script\s*>", | ||
| lambda m: "<script>" + minify_js(m.group(1)) + "</script>", |
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The updated regular expression correctly handles case-insensitivity and attributes in the opening <script> tag. However, the lambda function for replacement, lambda m: "<script>" + minify_js(m.group(1)) + "</script>", hardcodes the opening tag as <script>. This will strip all attributes from the original tag, such as src from external scripts.
For example, a tag like <script src="script.js"></script> would become <script></script>, which would prevent the script from loading and break the page.
To fix this, you should capture the opening and closing tags and reuse them in the replacement.
| r"(?is)<script\b[^>]*>(.*?)</script\s*>", | |
| lambda m: "<script>" + minify_js(m.group(1)) + "</script>", | |
| r"(?is)(<script\b[^>]*>)(.*?)(</script\s*>)", | |
| lambda m: m.group(1) + minify_js(m.group(2)) + m.group(3), |
| r"(?is)<style\b[^>]*>(.*?)</style\s*>", | ||
| lambda m: "<style>" + minify_css(m.group(1)) + "</style>", |
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Similar to the <script> tag handling, the replacement for <style> tags is hardcoded and will strip any attributes from the original tag (e.g., media="screen"). This could lead to incorrect styling on the page.
To fix this, you should also capture the opening and closing tags and reuse them in the replacement.
| r"(?is)<style\b[^>]*>(.*?)</style\s*>", | |
| lambda m: "<style>" + minify_css(m.group(1)) + "</style>", | |
| r"(?is)(<style\b[^>]*>)(.*?)(</style\s*>)", | |
| lambda m: m.group(1) + minify_css(m.group(2)) + m.group(3), |
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Potential fix for https://github.com/john-bampton/john-bampton.github.io/security/code-scanning/18
In general, to fix this type of problem you need a regex that is robust to HTML’s case-insensitivity and common syntax variants (attributes, whitespace), or better yet use an HTML parser. Given the constraints (only adjusting the shown snippet, and this is a minifier), the best approach is to update the regex for
<script>and<style>blocks to:re.IGNORECASE, andConcretely in
render.py, functionminify_html:<script>regex fromr"<script>(.*?)</script>"with onlyre.DOTALLto something liker"(?is)<script\b[^>]*>(.*?)</script\s*>". Using an inline(?is)flag makes the match case-insensitive and dot-all within this pattern, and allows attributes after the tag name and optional whitespace/garbage before the closing>.<style>regex fromr"<style>(.*?)</style>"with onlyre.DOTALLtor"(?is)<style\b[^>]*>(.*?)</style\s*>".These changes preserve current functionality (they still capture the inner script/style content and pass it to
minify_js/minify_css), but make the minifier work for uppercase tags and tags with attributes. No new imports are required; we only adjust the regex strings and can drop theflags=re.DOTALLargument since we are using inline flags.Suggested fixes powered by Copilot Autofix. Review carefully before merging.