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Changed logic behind identification of special template values #928

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Merged
michelebastione merged 2 commits into from
Feb 26, 2026
Merged

Changed logic behind identification of special template values #928

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ce34703
Changed logic behind special template cell values identification
michelebastione Feb 26, 2026
fb184ed
Minor adjustment
michelebastione Feb 26, 2026
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27 changes: 21 additions & 6 deletions src/MiniExcel.OpenXml/Templates/OpenXmlTemplate.Impl.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -377,7 +377,23 @@ await writer.WriteAsync($"<{prefix}sheetData>"
var rowInfo = _xRowInfos[rowNo];
var row = rowInfo.Row;

if (row.InnerText.Contains("@group"))
string specialCellType = "";
foreach (XmlNode c in row.GetElementsByTagName("c"))
{
specialCellType = c.InnerText switch
{
"@group" => "group",
"@endgroup" => "endgroup",
"@merge" or "@endmerge" => "merge",
var s when s.StartsWith("@header") => "header",
_ => ""
};

if (!string.IsNullOrEmpty(specialCellType))
break;
}
Comment on lines +380 to +394
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@gemini-code-assist gemini-code-assist bot Feb 26, 2026

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security-high high

This code block is responsible for identifying special template commands. The current implementation, however, processes these commands on cell content after user-provided data has been injected. This introduces a high-severity Template Injection vulnerability, as an attacker could provide data matching command strings (e.g., @group) to manipulate the template's execution logic or cause a denial of service. It is critical to identify commands from the original, unmodified template structure before any data replacement occurs. Furthermore, for improved readability, consider replacing the C# 11 list pattern ['@','h','e','a','d','e','r', ..] with a more explicit when clause using StartsWith().

                specialCellType = c.InnerText switch
                {
                    "@group" => "group",
                    "@endgroup" => "endgroup",
                    "@merge" or "@endmerge" => "merge",
                    var s when s.StartsWith("@header") => "header",
                    _ => ""
                };

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@michelebastione michelebastione Feb 26, 2026

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That's incorrect, data replacement already occurs after commands identification


if (specialCellType == "group")
{
groupingStarted = true;
hasEverGroupStarted = true;
Expand All @@ -386,7 +402,7 @@ await writer.WriteAsync($"<{prefix}sheetData>"
prevHeader = "";
continue;
}
else if (row.InnerText.Contains("@endgroup"))
else if (specialCellType == "endgroup")
{
if (cellIEnumerableValuesIndex >= cellIEnumerableValues.Count - 1)
{
Expand All @@ -403,13 +419,13 @@ await writer.WriteAsync($"<{prefix}sheetData>"
isFirstRound = false;
continue;
}
else if (row.InnerText.Contains("@header"))
else if (specialCellType == "header")
{
isHeaderRow = true;
}
else if (mergeCells)
{
if (row.InnerText.Contains("@merge") || row.InnerText.Contains("@endmerge"))
if (specialCellType == "merge")
{
mergeRowCount++;
continue;
Expand All @@ -418,8 +434,7 @@ await writer.WriteAsync($"<{prefix}sheetData>"

if (groupingStarted && !isCellIEnumerableValuesSet)
{
cellIEnumerableValues = rowInfo.CellIlListValues
?? rowInfo.CellIEnumerableValues.Cast<object>().ToList();
cellIEnumerableValues = rowInfo.CellIlListValues ?? rowInfo.CellIEnumerableValues.Cast<object>().ToList();
isCellIEnumerableValuesSet = true;
}

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