diff --git a/packages/commons/src/lib/spreadsheet/render_to_html.spec.ts b/packages/commons/src/lib/spreadsheet/render_to_html.spec.ts
index ab83c25898..dd3f10e26a 100644
--- a/packages/commons/src/lib/spreadsheet/render_to_html.spec.ts
+++ b/packages/commons/src/lib/spreadsheet/render_to_html.spec.ts
@@ -305,4 +305,117 @@ describe("renderSpreadsheetToHtml", () => {
         expect(html).toContain("text-align:center");
         expect(html).toContain("border-bottom:");
     });
+
+    it("sanitizes CSS injection in color values", () => {
+        const input = JSON.stringify({
+            version: 1,
+            workbook: {
+                sheetOrder: ["s1"],
+                styles: {},
+                sheets: {
+                    s1: {
+                        id: "s1",
+                        name: "Sheet1",
+                        hidden: 0,
+                        rowCount: 10,
+                        columnCount: 5,
+                        mergeData: [],
+                        cellData: {
+                            "0": {
+                                "0": {
+                                    v: "test",
+                                    s: {
+                                        bg: { rgb: "red;background:url(//evil.com/steal)" },
+                                        cl: { rgb: "#FFF;color:expression(alert(1))" }
+                                    }
+                                }
+                            }
+                        },
+                        rowData: {},
+                        columnData: {}
+                    }
+                }
+            }
+        });
+
+        const html = renderSpreadsheetToHtml(input);
+        expect(html).not.toContain("evil.com");
+        expect(html).not.toContain("expression");
+        expect(html).toContain("transparent");
+    });
+
+    it("sanitizes CSS injection in font-family", () => {
+        const input = JSON.stringify({
+            version: 1,
+            workbook: {
+                sheetOrder: ["s1"],
+                styles: {},
+                sheets: {
+                    s1: {
+                        id: "s1",
+                        name: "Sheet1",
+                        hidden: 0,
+                        rowCount: 10,
+                        columnCount: 5,
+                        mergeData: [],
+                        cellData: {
+                            "0": {
+                                "0": {
+                                    v: "test",
+                                    s: {
+                                        ff: "Arial;}</style><script>alert(1)</script>"
+                                    }
+                                }
+                            }
+                        },
+                        rowData: {},
+                        columnData: {}
+                    }
+                }
+            }
+        });
+
+        const html = renderSpreadsheetToHtml(input);
+        expect(html).not.toContain("<script>");
+        expect(html).not.toContain("</style>");
+        expect(html).toContain("font-family:Arial");
+    });
+
+    it("sanitizes CSS injection in border colors", () => {
+        const input = JSON.stringify({
+            version: 1,
+            workbook: {
+                sheetOrder: ["s1"],
+                styles: {},
+                sheets: {
+                    s1: {
+                        id: "s1",
+                        name: "Sheet1",
+                        hidden: 0,
+                        rowCount: 10,
+                        columnCount: 5,
+                        mergeData: [],
+                        cellData: {
+                            "0": {
+                                "0": {
+                                    v: "test",
+                                    s: {
+                                        bd: {
+                                            b: { s: 1, cl: { rgb: "#000;background:url(//evil.com)" } }
+                                        }
+                                    }
+                                }
+                            }
+                        },
+                        rowData: {},
+                        columnData: {}
+                    }
+                }
+            }
+        });
+
+        const html = renderSpreadsheetToHtml(input);
+        expect(html).not.toContain("evil.com");
+        expect(html).toContain("transparent");
+    });
 });
diff --git a/packages/commons/src/lib/spreadsheet/render_to_html.ts b/packages/commons/src/lib/spreadsheet/render_to_html.ts
index 243bbfed47..ca6a845acd 100644
--- a/packages/commons/src/lib/spreadsheet/render_to_html.ts
+++ b/packages/commons/src/lib/spreadsheet/render_to_html.ts
@@ -177,7 +177,7 @@ function renderSheet(sheet: IWorksheetData, styles: Record<string, IStyleData |
     for (let col = minCol; col <= maxCol; col++) {
         const colMeta = columnData[col];
         if (colMeta?.hd) continue;
-        const width = colMeta?.w ?? defaultWidth;
+        const width = isFiniteNumber(colMeta?.w) ? colMeta.w : defaultWidth;
         lines.push(`<col style="width:${width}px">`);
     }
     lines.push("</colgroup>");
@@ -188,7 +188,7 @@ function renderSheet(sheet: IWorksheetData, styles: Record<string, IStyleData |
         const rowMeta = rowData[row];
         if (rowMeta?.hd) continue;
 
-        const height = rowMeta?.h ?? defaultHeight;
+        const height = isFiniteNumber(rowMeta?.h) ? rowMeta.h : defaultHeight;
         lines.push(`<tr style="height:${height}px">`);
 
         for (let col = minCol; col <= maxCol; col++) {
@@ -329,10 +329,10 @@ function buildCssText(style: IStyleData | null): string {
             parts.push("text-decoration:line-through");
         }
     }
-    if (style.fs) parts.push(`font-size:${style.fs}pt`);
-    if (style.ff) parts.push(`font-family:${style.ff}`);
-    if (style.bg?.rgb) parts.push(`background-color:${style.bg.rgb}`);
-    if (style.cl?.rgb) parts.push(`color:${style.cl.rgb}`);
+    if (style.fs && isFiniteNumber(style.fs)) parts.push(`font-size:${style.fs}pt`);
+    if (style.ff) parts.push(`font-family:${sanitizeCssValue(style.ff)}`);
+    if (style.bg?.rgb) parts.push(`background-color:${sanitizeCssColor(style.bg.rgb)}`);
+    if (style.cl?.rgb) parts.push(`color:${sanitizeCssColor(style.cl.rgb)}`);
 
     if (style.ht != null) {
         const align = horizontalAlignToCss(style.ht);
@@ -374,7 +374,7 @@ function verticalAlignToCss(align: number): string | null {
 function appendBorderCss(parts: string[], property: string, border: IBorderStyleData | null | undefined): void {
     if (!border) return;
     const width = borderStyleToWidth(border.s);
-    const color = border.cl?.rgb ?? "#000";
+    const color = sanitizeCssColor(border.cl?.rgb ?? "#000");
     const style = borderStyleToCss(border.s);
     parts.push(`${property}:${width} ${style} ${color}`);
 }
@@ -395,6 +395,35 @@ function borderStyleToCss(style: number | undefined): string {
     }
 }
 
+/** Checks that a value is a finite number (guards against stringified payloads from JSON). */
+function isFiniteNumber(v: unknown): v is number {
+    return typeof v === "number" && Number.isFinite(v);
+}
+
+/**
+ * Sanitizes an arbitrary string for use as a CSS value by removing characters
+ * that could break out of a property (semicolons, braces, angle brackets, etc.).
+ */
+function sanitizeCssValue(value: string): string {
+    return value.replace(/[;<>{}\\/()'"]/g, "");
+}
+
+/**
+ * Validates a CSS color string. Accepts hex colors (#rgb, #rrggbb, #rrggbbaa),
+ * named colors (letters only), and rgb()/rgba()/hsl()/hsla() functional notation
+ * with safe characters. Returns "transparent" for anything that doesn't match.
+ */
+function sanitizeCssColor(value: string): string {
+    const trimmed = value.trim();
+    // Hex colors
+    if (/^#[0-9a-fA-F]{3,8}$/.test(trimmed)) return trimmed;
+    // Named colors (letters only, reasonable length)
+    if (/^[a-zA-Z]{1,30}$/.test(trimmed)) return trimmed;
+    // Functional notation: rgb(), rgba(), hsl(), hsla() — allow digits, commas, dots, spaces, %
+    if (/^(?:rgb|hsl)a?\([0-9.,\s%]+\)$/.test(trimmed)) return trimmed;
+    return "transparent";
+}
+
 // #endregion
 
 // #region Value formatting
@@ -414,7 +443,9 @@ function escapeHtml(text: string): string {
         .replace(/&/g, "&amp;")
         .replace(/</g, "&lt;")
         .replace(/>/g, "&gt;")
-        .replace(/"/g, "&quot;");
+        .replace(/"/g, "&quot;")
+        .replace(/'/g, "&#39;");
+    ;
 }
 
 // #endregion