Excelize is a Go language library for reading and writing Microsoft Excel spreadsheets. From 2.8.0 to 2.11.0, GetStyle's fill, border, and font extraction predicates check only upper bounds for attacker-controlled style-table indices. File.GetStyle relies on extractStyleCondFuncs predicates that allow negative FillID, BorderID, and FontID values to reach slice indexing. When a crafted styles.xml supplies a negative fillId, borderId, or fontId and the application reads the style, a negative identifier passes the upper-bound-only predicate and becomes a negative slice index, allowing an attacker to panic while reading cell styling. No fixed version is available as of this review.

Affected: Go: github.com/xuri/excelize/v2

## Summary

`File.GetStyle` indexes the fill, border and font tables with values taken straight out of `xl/styles.xml`, and the conditions gating those lookups check only the upper bound. A workbook whose `cellXfs` entry carries `fillId="-1"`, `borderId="-1"` or `fontId="-1"` reaches a negative slice index and panics. excelize has no `recover()`, so the panic leaves `GetStyle` and takes the calling process with it.

Same defect class as GHSA-48hm-4h8j-58fg, the negative shared-string index, in a different file. That one was fixed by adding the missing lower bound; these three sites still lack it.

## Where it is

`styles.go`, in `GetStyle`, lines 1683, 1686 and 1689:

```go xf := s.CellXfs.Xf[idx] if extractStyleCondFuncs["fill"](xf, s) { f.extractFills(s.Fills.Fill[*xf.FillID], s, style) } if extractStyleCondFuncs["border"](xf, s) { f.extractBorders(s.Borders.Border[*xf.BorderID], s, style) } if extractStyleCondFuncs["font"](xf, s) { style.Font = extractFont(s.Fonts.Font[*xf.FontID]) } ```

The conditions, at lines 1171 to 1185, bound only the top:

```go "fill": func(xf xlsxXf, s *xlsxStyleSheet) bool { return (xf.ApplyFill == nil || (xf.ApplyFill != nil && *xf.ApplyFill)) && xf.FillID != nil && s.Fills != nil && *xf.FillID < len(s.Fills.Fill) }, ```

`*xf.FillID < len(...)` is satisfied by any negative value. `FillID`, `BorderID` and `FontID` are `*int` unmarshalled directly from the `fillId`, `borderId` and `fontId` attributes, so the valu…