Office Open Xml ~upd~ Download -

Set a maximum decompression ratio (e.g., ZipFile.Extract with ExtractEntry limits). For generation, do not decompress untrusted archives. 4.3 Path Traversal in ZIP Entries Evil entries like ../../config/secret.xml inside a ZIP can overwrite files.

<!DOCTYPE doc [ <!ENTITY xxe SYSTEM "file:///etc/passwd"> ]> <w:p><w:r><w:t>&xxe;</w:t></w:r></w:p> Always disable external entities and DTDs in your XML parser. office open xml download

Critical note: Microsoft Office defaults to , whereas some open-source parsers prefer Strict . For maximum compatibility in download scenarios, target Transitional. 3. The "Download" Problem: Generation and Delivery 3.1 Two Primary Strategies | Strategy | Description | Pros | Cons | | :--- | :--- | :--- | :--- | | Template-based | Load a pre-created .docx template, replace placeholders (e.g., name ). | Preserves complex formatting. | Requires template management; large memory if using DOM. | | Programmatic build | Build XML trees (e.g., using DocumentBuilder libraries). | Full control; scalable. | Steeper learning curve for complex layouts. | 3.2 Performance Bottleneck: DOM vs. Streaming Most naive implementations load the entire document.xml into an XML DOM (Document Object Model). For a 50-page report, this may be ~10 MB; for a 500,000-row Excel sheet, this can exceed 2 GB of RAM. Set a maximum decompression ratio (e

– Write XML directly to the ZIP entry's output stream using a XmlWriter (or equivalent) without retaining the entire tree. using (var archive = new ZipArchive(stream

report.zip ├── [Content_Types].xml ├── _rels/ │ └── .rels ├── docProps/ │ ├── core.xml │ └── app.xml └── word/ ├── document.xml ├── styles.xml ├── _rels/ │ └── document.xml.rels └── media/ └── image1.png Logically, the file is composed of (XML, binary, image) linked by relationships using Relationship Id attributes. 2.2 Key Standards | Standard | Content | | :--- | :--- | | ECMA-376 1st ed. (2006) | Legacy "transitional" syntax. | | ISO/IEC 29500:2008 | Strict and transitional variants. | | ISO/IEC 29500:2016 | Added support for dynamic charts, accessibility features. |

var stream = new MemoryStream(); using (var archive = new ZipArchive(stream, ZipArchiveMode.Create, true)) // 1. [Content_Types].xml var ctEntry = archive.CreateEntry("[Content_Types].xml"); using (var ctWriter = new StreamWriter(ctEntry.Open())) ctWriter.Write(@"<?xml version='1.0' encoding='UTF-8'?> <Types xmlns='http://schemas.openxmlformats.org/package/2006/content-types'> <Default Extension='rels' ContentType='application/vnd.openxmlformats-package.relationships+xml'/> <Default Extension='xml' ContentType='application/xml'/> <Override PartName='/word/document.xml' ContentType='application/vnd.openxmlformats-officedocument.wordprocessingml.document.main+xml'/> </Types>"); // 2. Relationships (.rels) var relsEntry = archive.CreateEntry("_rels/.rels"); using (var relsWriter = new StreamWriter(relsEntry.Open())) relsWriter.Write(@"<?xml version='1.0'?> <Relationships xmlns='http://schemas.openxmlformats.org/package/2006/relationships'> <Relationship Id='rId1' Type='http://schemas.openxmlformats.org/officeDocument/2006/relationships/officeDocument' Target='word/document.xml'/> </Relationships>");