GroupDocs.Conversion for .NET 26.1 Release Notes

There are 8 features, improvements, and bug fixes in this release.

Adds full FlatOpc (flat XML) format support for import and export, and delivers extensive stability and security improvements—including fixes for conversion accuracy, dependency handling, and SSRF/NTLM vulnerabilities.

Full list of changes in this release

Major Features

• FlatOpc (Flat XML) Support: Full import and export of the FlatOpc format for Word, Excel, and PowerPoint documents, enabling seamless conversion to and from flat XML representations.

• Improved FlatOpc Conversion Accuracy: Fixed conversion issues for Excel FlatOpc files to SVG/SVGZ and resolved PDF‑to‑Excel image handling problems, delivering reliable output quality across formats.

• Enhanced Security: Patched Server‑Side Request Forgery (SSRF) and NTLM credential leakage vulnerabilities, safeguarding conversion processes from malicious document references.

• Robust Dependency Management: Restored the required Aspose.Drawing libraries, eliminating runtime errors when converting image and Visio files.

• Consistent Document Behavior: Corrected automatic Table of Contents updates and stamp handling with margin settings, giving users precise control over the content of converted documents.

Public API and backward incompatible changes

1. Loading options – WordProcessingLoadOptions.Format

The Format property now accepts the new enum value WordProcessingFileType.FlatOpc to load Word documents stored as a single XML file (Flat OPC).

• Reference: WordProcessingLoadOptions

2. Loading options – SpreadsheetLoadOptions.Format

The Format property now accepts the new enum value SpreadsheetFileType.FlatOpc to load Excel spreadsheets stored as a single XML file (Flat OPC).

• Reference: SpreadsheetLoadOptions

3. Convert options – WordProcessingConvertOptions.Format

The Format property now supports WordProcessingFileType.FlatOpc, enabling conversion to Flat OPC Word documents.

• Reference: WordProcessingConvertOptions

4. Convert options – SpreadsheetConvertOptions.Format

The Format property now supports SpreadsheetFileType.FlatOpc, enabling conversion to Flat OPC Excel spreadsheets.

• Reference: SpreadsheetConvertOptions

Code samples

1. Convert Word Flat OPC 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 DOCX to Word Flat OPC

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 Excel Flat OPC 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 XLSX to Excel Flat OPC

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);
}

Migration guidance

No deprecated APIs were removed in this release. Existing code continues to work; simply set the Format property to the new FlatOpc enum values where Flat OPC support is required.

Release Notes Entries

CONVERSIONNET-8164: Fix SSRF and NTLM credential leak vulnerabilities in document conversion

Breaking change

In the following classes, the SkipExternalResources property is changed from default false to true:

• WordProcessingLoadOptions

• PresentationLoadOptions

• EmailLoadOptions

• WebLoadOptions

• SvgLoadOptions