What’s new in GroupDocs.Conversion for .NET 26.1 (January 2026)

Category Issue Description
Feature CONVERSIONNET-8080 Full import and export support for the FlatOpc (Flat XML) format for Word, Excel, and PowerPoint documents.
Improvement CONVERSIONNET-4551 Fixed incorrect conversion of PDFs that contain images to Excel worksheets.
Improvement CONVERSIONNET-8147 Restored the required Aspose.Drawing assembly, eliminating runtime Could not load file or assembly errors when processing image‑ and Visio‑based files.
Improvement CONVERSIONNET-8153 Corrected stamp handling so that stamps are no longer replaced with the literal “Draft” text when MarginSettings are enabled during PDF conversion.
Improvement CONVERSIONNET-8157 Fixed diagram watermark resource loading after code obfuscation.
Security fix CONVERSIONNET-8164 Patched Server‑Side Request Forgery (SSRF) and NTLM credential‑leak vulnerabilities. The SkipExternalResources property now defaults to true for several load‑option classes.
Improvement CONVERSIONNET-8170 Table of Contents is no longer updated automatically unless UpdateFields is explicitly set to true.
Improvement CONVERSIONNET-8185 Resolved conversion of Excel FlatOpc files to SVG and SVGZ formats.

Major highlights

  • FlatOpc (Flat XML) support – load and save Word, Excel, and PowerPoint files as a single XML representation.
  • Conversion accuracy – reliable Excel FlatOpc → SVG/SVGZ output and correct PDF‑to‑Excel image extraction.
  • Enhanced security – SSRF and NTLM credential leaks are mitigated; external resources are skipped by default.
  • Robust dependencies – the missing Aspose.Drawing dependency is bundled, preventing assembly‑load failures.
  • Predictable document behavior – TOC updates and stamp rendering now respect the explicit conversion settings.

Public API changes (backward‑compatible)

The Format property of several load‑ and convert‑option classes now accepts new enum values for FlatOpc handling.

Class Property New enum value
WordProcessingLoadOptions Format WordProcessingFileType.FlatOpc
SpreadsheetLoadOptions Format SpreadsheetFileType.FlatOpc
WordProcessingConvertOptions Format WordProcessingFileType.FlatOpc
SpreadsheetConvertOptions Format SpreadsheetFileType.FlatOpc

Note: No APIs were removed. Existing code continues to work; simply assign the new FlatOpc enum value where needed.

Code samples

1. Convert a Word FlatOpc file to PDF

using GroupDocs.Conversion;
using GroupDocs.Conversion.FileTypes;
using GroupDocs.Conversion.Options.Convert;
using GroupDocs.Conversion.Options.Load;

var loadOptions = new WordProcessingLoadOptions
{
    Format = WordProcessingFileType.FlatOpc
};

using (var converter = new Converter("document.xml", () => loadOptions))
{
    var options = new PdfConvertOptions();
    converter.Convert("output.pdf", options);
}

2. Convert a DOCX file to Word FlatOpc

using GroupDocs.Conversion;
using GroupDocs.Conversion.FileTypes;
using GroupDocs.Conversion.Options.Convert;

using (var converter = new Converter("document.docx"))
{
    var options = new WordProcessingConvertOptions
    {
        Format = WordProcessingFileType.FlatOpc
    };
    converter.Convert("output.word.xml", options);
}

3. Convert an Excel FlatOpc file to PDF

using GroupDocs.Conversion;
using GroupDocs.Conversion.FileTypes;
using GroupDocs.Conversion.Options.Convert;
using GroupDocs.Conversion.Options.Load;

var loadOptions = new SpreadsheetLoadOptions
{
    Format = SpreadsheetFileType.FlatOpc
};

using (var converter = new Converter("spreadsheet.xml", () => loadOptions))
{
    var options = new PdfConvertOptions();
    converter.Convert("output.pdf", options);
}

4. Convert an XLSX file to Excel FlatOpc

using GroupDocs.Conversion;
using GroupDocs.Conversion.FileTypes;
using GroupDocs.Conversion.Options.Convert;

using (var converter = new Converter("spreadsheet.xlsx"))
{
    var options = new SpreadsheetConvertOptions
    {
        Format = SpreadsheetFileType.FlatOpc
    };
    converter.Convert("output.excel.xml", options);
}

How to get the update

  • NuGet – Upgrade to the latest package:

    Install-Package GroupDocs.Conversion -Version 26.1.0

    (or update via the NuGet UI in Visual Studio).

  • Direct download – Assemblies for .NET 6 / .NET Framework can be downloaded from the official GroupDocs release page once it is published.

Resources