The "Protect Worksheet" functionality in Mathsoft Mathcad 12 through 13.1, and PTC Mathcad 14, implements file access restrictions via a protection element in a gzipped XML file, which allows attackers to bypass these restrictions by removing this element.

Mathcad 12 through 13.1 allows local users to bypass the security features by directly accessing or editing the XML representation of the worksheet with a text editor or other program, which allows attackers to (1) bypass password protection by replacing the password field with a hash of a known password, (2) modify timestamps to avoid detection of modifications, (3) remove locks by removing the "is-locked" attribute, and (4) view locked data, which is stored in plaintext.