CairoSVG: Quadratic-time DoS parsing a crafted SVG <path>

CairoSVG is an SVG converter based on Cairo, a 2D graphics library. Prior to 2.9.1, rendering an attacker-controlled SVG with a path containing many segments can cause quadratic CPU consumption in cairosvg/path.py. The path tokenizer repeatedly slices and rescans the remaining path data, while draw_markers drains node.vertices with node.vertices.pop(0), causing repeated linear-time work. The svg2png, svg2pdf, and svg2ps APIs reach these operations during ordinary rendering, allowing a sub-megabyte SVG to consume substantial CPU and deny service to a rendering application. This issue is fixed in version 2.9.1.