XSS lets attackers run scripts in a victim's browser, enabling data theft or account abuse; contextual output encoding and CSP reduce risk.
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Background for this topic.
Cross-site scripting (XSS) is a web-application flaw in which attacker-controlled input is interpreted as script in another user’s browser. It can be stored in application data, reflected in an immediate response, or introduced by unsafe client-side code (DOM-based XSS). The script runs in the affected site’s origin, so it may read page content, alter requests, or perform actions available to the victim; impact depends on the victim’s privileges and the application’s defenses.
The primary mitigation is context-aware output encoding: treat untrusted data as text when inserting it into HTML, attributes, URLs, JavaScript, or CSS, and use safe DOM APIs such as textContent rather than unsafe HTML insertion. If user-authored HTML is required, apply a well-tested HTML sanitizer. A restrictive Content Security Policy can limit exploitability but is defense in depth, not a substitute for correct encoding. HttpOnly cookies can reduce direct cookie theft, but do not prevent XSS from performing in-session actions.
Weekly headline count for the current query.
Zimbra is urging customers to apply updates to address a critical security vulnerability impacting the Classic Web Client that could result in arbitrary code execution
Zimbra addressed a critical stored XSS vulnerability in its Classic Web Client that lets malicious emails execute code when opened. Zimbra has released version 10.1.19 to fix a critical stored XSS vulnerability in its Classic Web Client, which is widely used to access Zimbra Collaboration. The flaw, which has not yet received a CVE ID, […]
The Zimbra security team urged customers to patch a critical vulnerability affecting the Classic Web Client used to access the Zimbra Collaboration suite. [...]
Police arrested the alleged admin of XSS.is, a major cybercrime forum whose trusted escrow service helped power the underground economy. On 22 July 2025, French and Ukrainian police arrested a 38-year-old man in Kyiv and shut down XSS.is, the most influential Russian-language cybercrime forum of the past decade. Europol, which coordinated the operation under the […]
Microsoft has patched an actively exploited Exchange Server vulnerability that allows threat actors to execute arbitrary JavaScript code in cross-site scripting (XSS) attacks targeting Outlook Web Access users. [...]
CVE-2026-42897 stems from a cross-site scripting (XSS) vulnerability and can allow an attacker to compromise Outlook Web Access (OWA) mailboxes.
On Thursday, Microsoft shared mitigations for a high-severity Exchange Server vulnerability exploited in attacks that allow threat actors to execute arbitrary code via cross-site scripting (XSS) while targeting Outlook on the web users. [...]
Microsoft has disclosed a new security vulnerability impacting on-premise versions of Exchange Server that it said has come under active exploitation in the wild
Over 10,000 Zimbra Collaboration Suite (ZCS) instances exposed online are vulnerable to ongoing attacks exploiting a cross-site scripting (XSS) security flaw. [...]
Germany's Federal Criminal Police Office (aka BKA or the Bundeskriminalamt) has unmasked the real identities of two of the key figures associated with the now-defunct REvil (aka Sodinokibi) ransomware-as-a-service (RaaS) operation
Cybersecurity researchers have disclosed a vulnerability in Anthropic's Claude Google Chrome Extension that could have been exploited to trigger malicious prompts simply by visiting a web page
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has urged government agencies to apply patches for two security flaws impacting Synacor Zimbra Collaboration Suite (ZCS) and Microsoft Office SharePoint, stating they have been actively exploited in the wild
CISA has ordered U.S. government agencies to secure their servers against an actively exploited vulnerability in the Zimbra Collaboration Suite (ZCS). [...]
PLUS: Firefox adds XSS protection; Leadership turnover at CISA; FTC exempts some data collection Infosec In Brief DNS vulnerabilities are being addressed 84 percent faster in the UK public sector thanks to an automated vulnerability scanning system established as part of a program kicked off early last year.…
Cybersecurity researchers have disclosed a cross-site scripting (XSS) vulnerability in the web-based control panel used by operators of the StealC information stealer, allowing them to gather crucial insights on one of the threat actors using the malware in their operations
A cross-site scripting (XSS) flaw in the web-based control panel used by operators of the StealC info-stealing malware allowed researchers to observe active sessions and gather intelligence on the attackers' hardware. [...]
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has updated its Known Exploited Vulnerabilities (KEV) catalog to include a security flaw impacting OpenPLC ScadaBR, citing evidence of active exploitation
A now patched security vulnerability in Zimbra Collaboration was exploited as a zero-day earlier this year in cyber attacks targeting the Brazilian military
On July 22, 2025, the European police agency Europol said a long-running investigation led by the French Police resulted in the arrest of a 38-year-old administrator of XSS, a Russian-language cybercrime forum with more than 50,000 members. The action has triggered an ongoing frenzy of speculation and panic among XSS denizens about the identity of the unnamed suspect, but the consensus is that he is a pivotal figure in the crime forum scene who goes by the hacker handle "Toha." Here's a deep dive on what's knowable about Toha, and a short stab at who got nabbed.
React conquered XSS? Think again. That's the reality facing JavaScript developers in 2025, where attackers have quietly evolved their injection techniques to exploit everything from prototype pollution to AI-generated code, bypassing the very frameworks designed to keep applications secure