Persistent XSS in Markdown Files Enables Remote Code Execution

Anote 1.0 contains a persistent cross-site scripting vulnerability that allows attackers to execute arbitrary code by injecting malicious payloads into markdown files stored within the application. Attackers can craft malicious markdown files with embedded JavaScript that executes system commands when opened, enabling remote code execution on the victim's computer.

Casky was already ahead

This CVE exploits attack patterns that Casky's 301matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

Anote 1.0 contains a persistent cross-site scripting (XSS) vulnerability that allows attackers to inject malicious JavaScript payloads into markdown files stored within the application. When victims open these compromised files, the embedded scripts execute with the privileges of the application, potentially escalating to remote code execution on the victim's system. This vulnerability affects any organization or individual using Anote 1.0 to store or share markdown documentation, creating a supply-chain-like risk where trusted document repositories become vectors for code injection attacks.

Casky's 301 mapped skills leverage Claude AI's extended reasoning to detect the attack patterns underlying this vulnerability across MITRE ATT&CK techniques TA0001 (Initial Access) and TA0043 (Reconnaissance). Practitioners using Casky would identify detection signatures for CWE-79 violations: suspicious markdown syntax containing script tags, event handlers (onclick, onload), or encoded JavaScript within document metadata. The platform's skill set helps security teams recognize how attackers progress from reconnaissance—identifying Anote deployments and user bases—through initial access via socially-engineered markdown files. Findings would highlight suspicious file modifications, execution of scripts from document processing contexts, and process spawning from markdown rendering engines, enabling defenders to catch exploitation attempts before system compromise.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

301 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2021-47963.

analyzing-apt-group-with-mitre-navigator

threat intelligence · low

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analyzing-campaign-attribution-evidence

threat intelligence · low

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analyzing-certificate-transparency-for-phishing

threat intelligence · low

Run

MITRE ATT&CK Techniques

TA0001 TA0043

Investigate the attack patterns behind CVE-2021-47963

Casky has 301 skills that investigate the attack patterns behind CVE-2021-47963. Run one and get CVSS-scored findings in 3 minutes.

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