Contrib.social

The XSS filter should allow more HTML entities

Open on Drupal.org →
Created on 10 September 2019, over 4 years ago
Updated 14 February 2023, over 1 year ago

Problem/Motivation

Xss:filter does not recognize HTML entities starting with &#x1 as well-formed.
Example: 𝔷 𝑙 𝑥 🂡
For more entities see https://www.compart.com/en/unicode/html

// Decimal numeric entities.
$string = preg_replace('/&#([0-9]+;)/', '&#\1', $string);
// Hexadecimal numeric entities.
$string = preg_replace('/&#[Xx]0*((?:[0-9A-Fa-f]{2})+;)/', '&#x\1', $string);

For example '🂡' (decimal) and '🂡' (hexadecimal) are the ace of spades symbols. Both should be valid.
The current regular expressions match '🂡' but does not match '🂡'.

Proposed resolution

Update Regex to accept also &#x1 entities.

Remaining tasks

Review for security consequences.

User interface changes

None.

API changes

None.

Data model changes

None.

🐛 Bug report
Status

Needs work

Version

10.1 ✨

Component
Base  →

Last updated less than a minute ago

Created by

🇨🇿Czech Republic martin_klima

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  • Needs framework manager review

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Comments & Activities

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It's likely this issue predates Contrib.social: some issue and comment data are missing.

  • Comment over 1 year ago →
    🇺🇸United States smustgrave

    Tagging for framework manager and security review for their thoughts on this.

  • Status changed to Needs work over 1 year ago
  • Comment over 1 year ago →
    🇺🇸United States greggles Denver, Colorado, USA

    Moving to needs work - in the issue summary and comments I don't see any research about what characters are or aren't safe from the perspective of causing XSS. Ideally there is a definitive source we can reference to help us figure that out. The resources I know that had that kind of information are now offline so I'm not totally sure where to go in 2023.

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