scm/define-stencil-commands.scm in LilyPond through 2.20.0, and 2.21.x through 2.21.4, when -dsafe is used, lacks restrictions on embedded-ps and embedded-svg, as demonstrated by including dangerous PostScript code.

LilyPond before 2.24 allows attackers to bypass the -dsafe protection mechanism via output-def-lookup or output-def-scope, as demonstrated by dangerous Scheme code in a .ly file that causes arbitrary code execution during conversion to a different file format. NOTE: in 2.24 and later versions, safe mode is removed, and the product no longer tries to block code execution when external files are used.