CVE-2026-26028

The record

CryptPad is an end-to-end encrypted collaborative office suite. In versions prior to 2026.2.0, the HTML sanitizer in Diffmarked.js can be bypassed due to incomplete attribute filtering on restricted tags. The sanitizer validates only the src attribute of <iframe>, <video>, and <audio> elements, leaving all other attributes unchecked. As a result, an attacker can inject arbitrary HTML through srcdoc, completely defeating CryptPad's intended bounce sandboxing and enabling link injection or other interactive content within user-controlled documents. The root cause lies in how the sanitizer classifies and enforces tag restrictions: although it defines both forbidden and restricted tag lists, <iframe> is treated as "restricted" rather than "forbidden." Enforcement then inspects only the src attribute, so pairing a benign blob: src with a malicious srcdoc results in unrestricted rendering. This issue has been fixed in version 2026.2.0.

Affected packages

Related vulnerabilities

• GHSA-g2g4-47gv-p72v CryptPad has a Sanitizer Bypass in Diffmarked.js that Allows Arbitrary HTML Injection and… Same vulnerability
• CVE-2026-96379 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96382 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96368 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96361 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96362 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96360 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
• CVE-2026-96357 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79