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Fix over-blocking of safe URLs by the unsafe link filter #1131

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Merged
colinodell merged 2 commits into from
Jul 12, 2026
+33 −1
Merged

Fix over-blocking of safe URLs by the unsafe link filter #1131

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e910835
Add tests demonstrating unsafe link filter over-blocking
GrahamCampbell Jul 12, 2026
4334381
Anchor all REGEX_UNSAFE_PROTOCOL alternatives to the start of the URL
GrahamCampbell Jul 12, 2026
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2 changes: 1 addition & 1 deletion src/Util/RegexHelper.php
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Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,7 @@ final class RegexHelper
'|' . '\((' . self::PARTIAL_ESCAPED_CHAR . '|[^()\x00])*+\))';

public const REGEX_PUNCTUATION = '/^[\p{P}\p{S}]/u';
public const REGEX_UNSAFE_PROTOCOL = '/^javascript:|vbscript:|file:|data:/i';
public const REGEX_UNSAFE_PROTOCOL = '/^(?:javascript|vbscript|file|data):/i';
public const REGEX_SAFE_DATA_PROTOCOL = '/^data:image\/(?:png|gif|jpeg|webp)/i';
public const REGEX_NON_SPACE = '/[^ \t\f\v\r\n]/';

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32 changes: 32 additions & 0 deletions tests/unit/Util/RegexHelperTest.php
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Expand Up @@ -402,6 +402,38 @@ public static function blockTypesWithInvalidCloserRegexes(): iterable
yield [8];
}

/**
* @dataProvider dataForTestIsLinkPotentiallyUnsafe
*/
#[DataProvider('dataForTestIsLinkPotentiallyUnsafe')]
public function testIsLinkPotentiallyUnsafe(string $url, bool $expected): void
{
$this->assertSame($expected, RegexHelper::isLinkPotentiallyUnsafe($url));
}

/**
* @return iterable<array<mixed>>
*/
public static function dataForTestIsLinkPotentiallyUnsafe(): iterable
{
return [
// Dangerous leading schemes are unsafe
['javascript:alert(1)', true],
['JAVASCRIPT:alert(1)', true],
['vbscript:msgbox(1)', true],
['file:///etc/passwd', true],
['data:text/html,<script>alert(1)</script>', true],
['data:image/svg+xml,<svg onload=alert(1)>', true],
// Safe data: images are allowed
['data:image/png;base64,iVBORw0KGgo=', false],
// URLs merely containing those schemes elsewhere are safe
['https://example.com/view?src=data:image/png', false],
['https://example.com/download?to=file:report', false],
['https://example.com/wiki/vbscript:_basics', false],
['https://example.com/ok', false],
];
}

private function assertRegexMatches(string $pattern, string $string, string $message = ''): void
{
if (\method_exists($this, 'assertMatchesRegularExpression')) {
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