jsPDF is a library to generate PDFs in JavaScript. Prior to 4.1.0, the addJS method in the jspdf Node.js build utilizes a shared module-scoped variable (text) to store JavaScript content. When used in a concurrent environment (e.g., a Node.js web server), this variable is shared across all requests. If multiple requests generate PDFs simultaneously, the JavaScript content intended for one user may be overwritten by a subsequent request before the document is generated. This results in Cross-User Data Leakage, where the PDF generated for User A contains the JavaScript payload (and any embedded sensitive data) intended for User B. Typically, this only affects server-side environments, although the same race conditions might occur if jsPDF runs client-side. The vulnerability has been fixed in jsPDF@4.1.0.