Excelize: Unbounded <col max> attribute is loaded with no MaxColumns check and expanded per-column by flatCols(), so any column mutator hangs or OOMs the process

Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.1.0 to 2.11.0, flatCols expands file-loaded column ranges without validating Min and Max against the worksheet column limit. SetColWidth reaches flatCols, which expands xlsxCol.Min through xlsxCol.Max without enforcing MaxColumns. When a crafted worksheet supplies an oversized col max attribute and the application invokes a column mutator, flatCols performs a deep copy and append for every attacker-selected column number, allowing an attacker to consume excessive CPU and memory or trigger OOM. No fixed version is available as of this review.