probe-image-size: Quadratic-time Denial of Service in the SVG Parser

probe-image-size gets image dimensions without downloading the entire file. Prior to 7.4.0, lib/parse_sync/svg.js and lib/parse_stream/svg.js use the searching regular expression /<[-_.:a-zA-Z0-9][^>]*>/, which repeatedly scans to the end of input when attacker-controlled data contains many less-than characters without a closing greater-than character. The synchronous parser converts and scans the full supplied buffer without an input cap, while the streaming parser reparses the complete accumulated SVG prefix for every received chunk. The probe.sync(), probe(stream), and probe(url) entry points can therefore block the Node.js event loop at full CPU, and attacker-controlled chunking can amplify the streaming cost. This issue is fixed in version 7.4.0.