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#6233 Improve css validation #6234

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#6233 Improve css validation #6234

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3 changes: 2 additions & 1 deletion extension/js/common/platform/xss.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -49,7 +49,7 @@ export class Xss {
private static ADD_ATTR = ['email', 'page', 'addurltext', 'longid', 'index', 'target', 'fingerprint', 'cryptup-data'];
private static FORBID_ATTR = ['background'];
private static HREF_REGEX_CACHE: RegExp | undefined;
private static FORBID_CSS_STYLE = /z-index:[^;]+;|position:[^;]+;|background[^;]+;/g;
private static FORBID_CSS_STYLE = /z-index:[^;]+(?=;|$)|position:[^;]+(?=;|$)|background[^;]+(?=;|$)/gi;
private static EMOJI_REGEX = /(?![*#0-9]+)[\p{Emoji}\p{Emoji_Modifier}\p{Emoji_Component}\p{Emoji_Modifier_Base}\p{Emoji_Presentation}]/gu;

public static sanitizeRender = (selector: string | HTMLElement | JQuery, dirtyHtml: string) => {
Expand Down Expand Up @@ -118,6 +118,7 @@ export class Xss {
const style = node.getAttribute('style')?.toLowerCase();
if (style && (style.includes('url(') || style.includes('@import'))) {
node.removeAttribute('style'); // don't want any leaks through css url()
return; // stop processing: do not re-add any part of this style attribute
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@sosnovsky sosnovsky May 29, 2026

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if return will be executed here, then all next checks will be skipped?

so if style property includes some URL, then other checks for node.tagName === 'IMG' and node.tagName === 'A' won't be executed?
for example, <img src="https://example.com/tracker.png" style="background-image: url(https://example.com/bg.png)"> will return <img src="https://example.com/tracker.png"> - style property removed, but remote image is loaded

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@martgil martgil May 29, 2026

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Yes, but I realize I should formulate even better logic to fix this rather than what's current. BRB.

}
// strip css styles that could use to overlap with the extension UI
if (style && Xss.FORBID_CSS_STYLE.test(style)) {
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