CVE-2026-35208: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in lichess-org lila
CVE-2026-35208 is a cross-site scripting (XSS) vulnerability in the lichess-org lila platform. Approved streamers can inject arbitrary HTML into the /streamer page and the homepage Live streams widget by placing markup in their Twitch or YouTube stream titles. Although a Content Security Policy (CSP) blocks inline script execution, the vulnerability still allows server-side HTML injection. To exploit this, an attacker only needs a normal approved streamer account, which requires minimal criteria such as account age and game count or verification. The issue is fixed in commit 0d5002696ae705e1888bf77de107c73de57bb1b3. The CVSS 4. 0 base score is 5. 3, indicating medium severity.
AI Analysis
Technical Summary
The vulnerability arises because lichess.org renders streamer platform titles containing user-controlled markup directly into the UI without sufficient neutralization. Approved streamers, who meet basic account requirements and receive moderator approval, can embed arbitrary HTML in their Twitch or YouTube stream titles. This HTML is then injected into the /streamer page and the Live streams widget on the homepage. While CSP prevents inline script execution, the server-side injection of HTML remains a risk. The vulnerability is identified as CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-116 (Improper Encoding or Escaping of Output). The issue is resolved in commit 0d5002696ae705e1888bf77de107c73de57bb1b3.
Potential Impact
An attacker with an approved streamer account can inject arbitrary HTML into public-facing pages on lichess.org, potentially affecting users who view the Live streams widget or streamer pages. Although inline scripts are blocked by CSP, the injection of HTML could still lead to UI manipulation or other client-side impacts. No elevated privileges beyond a normal approved streamer profile are required. There are no known exploits in the wild at this time.
Mitigation Recommendations
This vulnerability is fixed in lichess-org lila as of commit 0d5002696ae705e1888bf77de107c73de57bb1b3. Users and administrators should update to this commit or a later version to remediate the issue. Since this is not a cloud service, patching the affected software version is necessary. No additional mitigation steps are indicated by the vendor advisory.
CVE-2026-35208: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in lichess-org lila
Description
CVE-2026-35208 is a cross-site scripting (XSS) vulnerability in the lichess-org lila platform. Approved streamers can inject arbitrary HTML into the /streamer page and the homepage Live streams widget by placing markup in their Twitch or YouTube stream titles. Although a Content Security Policy (CSP) blocks inline script execution, the vulnerability still allows server-side HTML injection. To exploit this, an attacker only needs a normal approved streamer account, which requires minimal criteria such as account age and game count or verification. The issue is fixed in commit 0d5002696ae705e1888bf77de107c73de57bb1b3. The CVSS 4. 0 base score is 5. 3, indicating medium severity.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability arises because lichess.org renders streamer platform titles containing user-controlled markup directly into the UI without sufficient neutralization. Approved streamers, who meet basic account requirements and receive moderator approval, can embed arbitrary HTML in their Twitch or YouTube stream titles. This HTML is then injected into the /streamer page and the Live streams widget on the homepage. While CSP prevents inline script execution, the server-side injection of HTML remains a risk. The vulnerability is identified as CWE-79 (Improper Neutralization of Input During Web Page Generation) and CWE-116 (Improper Encoding or Escaping of Output). The issue is resolved in commit 0d5002696ae705e1888bf77de107c73de57bb1b3.
Potential Impact
An attacker with an approved streamer account can inject arbitrary HTML into public-facing pages on lichess.org, potentially affecting users who view the Live streams widget or streamer pages. Although inline scripts are blocked by CSP, the injection of HTML could still lead to UI manipulation or other client-side impacts. No elevated privileges beyond a normal approved streamer profile are required. There are no known exploits in the wild at this time.
Mitigation Recommendations
This vulnerability is fixed in lichess-org lila as of commit 0d5002696ae705e1888bf77de107c73de57bb1b3. Users and administrators should update to this commit or a later version to remediate the issue. Since this is not a cloud service, patching the affected software version is necessary. No additional mitigation steps are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-04-01T18:48:58.937Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69d417e60a160ebd92da7f7c
Added to database: 4/6/2026, 8:30:30 PM
Last enriched: 4/6/2026, 8:46:07 PM
Last updated: 4/6/2026, 10:41:43 PM
Views: 5
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.