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High Severity

Attachment: HTML smuggling with auto-downloaded file

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Description

HTML attachments containing files that are automatically downloaded with Javascript.

References

Sublime Security
Created Aug 17th, 2023 • Last updated Aug 21st, 2023
Feed Source
Sublime Core Feed
Source
GitHub
type.inbound
and any(attachments,
        (
          .file_extension in~ ("html", "htm", "shtml", "dhtml")
          or .file_extension in~ $file_extensions_common_archives
          or .file_type == "html"
        )
        and any(file.explode(.),
                any(.scan.javascript.identifiers, strings.ilike(., 'click'))
                and any(.scan.javascript.identifiers, strings.ilike(., 'addEventListener'))
                and (
                  length(filter(.scan.javascript.identifiers,
                                strings.like(., "document", "write", "atob")
                         )
                  ) == 3
                  // usage: document['write'](atob)
                  or any(.scan.strings.strings, strings.ilike(., "*document*write*atob*"))
                  // usage: some_var = atob();
                  or any(.scan.strings.strings, strings.ilike(., "*=*atob*;"))
                  // usage: obfuscating "atob"
                  or any(.scan.javascript.identifiers, strings.ilike(., '*ato\u0062*'))
                  // usage: document.head.insertAdjacentHTML("beforeend", atob(...
                  or any(.scan.strings.strings,
                         strings.ilike(.,
                                       "*document*write*atob*",
                                       "*document*insertAdjacentHTML*atob*"
                         )
                  )
                )
        )
)

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