The Glyph Substitution Table (GSUB) is a component of OpenType font technology that defines how certain characters are replaced with alternate glyphs during text rendering. This table enables advanced typographic features such as ligatures, contextual alternates, and language-specific forms by mapping character sequences to specific glyph substitutions. In cybersecurity, understanding GSUB tables can be relevant when analyzing malicious documents or obfuscated scripts that use custom fonts to disguise code or text. Attackers may exploit font substitution to evade detection or to manipulate how information is displayed to users, making GSUB analysis a useful skill in document forensics and threat analysis.