Attachment: Embedded Javascript in SVG file

Severity: high
Type: rule
Source: github.com/sublime-security/sublime-rules

Javascript inside SVG files can be used to smuggle malicious payloads or execute scripts.

Threat classification

Sublime's own taxonomy (not MITRE ATT&CK).

Category	Values
Attack types	Malware/Ransomware
Tactics and techniques	Scripting

Event coverage

Message attribute
attachments (collection)
type

Rule body MQL

type.inbound
and any(attachments,
        (
          (
            .file_extension in~ ("svg", "svgz")
            or .content_type in~ ("image/svg+xml")
            or .file_type == "svg"
          )
          and (
            strings.ilike(file.parse_text(.,
                                          encodings=[
                                            "ascii",
                                            "utf8",
                                            "utf16-le"
                                          ]
                          ).text,
                          "*onload*",
                          "*window.location.href*",
                          "*onerror*",
                          "*CDATA*",
                          "*<script*",
                          "*</script*",
                          "*atob*",
                          "*location.assign*",
                          "*decodeURIComponent*"
            )
            or regex.icontains(file.parse_text(.,
                                               encodings=[
                                                 "ascii",
                                                 "utf8",
                                                 "utf16-le"
                                               ]
                               ).text,
                               '<iframe[^\>]+src\s*=\s*\"data:[^\;]+;base64,'
            )
            or any(beta.scan_base64(file.parse_text(.).text,
                                    encodings=["ascii", "utf8", "utf16-le"]
                   ),
                   strings.ilike(.,
                                 "*onload*",
                                 "*window.location.href*",
                                 "*onerror*",
                                 "*CDATA*",
                                 "*<script*",
                                 "*</script*",
                                 "*atob*",
                                 "*location.assign*",
                                 "*decodeURIComponent*"
                   )
            )
          )
        )
        or (
          (
            .file_extension in $file_extensions_common_archives
            or .file_type == "gz"
            or .content_type == "application/x-gzip"
          )
          and any(file.explode(.),
                  (
                    .file_extension in~ ("svg", "svgz")
                    or .flavors.mime == "image/svg+xml"
                  )
                  and any(.scan.strings.strings,
                          strings.ilike(.,
                                        "*onload*",
                                        "*window.location.href*",
                                        "*onerror*",
                                        "*CDATA*",
                                        "*<script*",
                                        "*</script*",
                                        "*atob*",
                                        "*location.assign*",
                                        "*decodeURIComponent*"
                          )
                  )
          )
        )
)

Detection logic

Scope: inbound message.

Javascript inside SVG files can be used to smuggle malicious payloads or execute scripts.

inbound message
any of attachments where any holds:
- all of:
  - any of:
    
    .file_extension in ('svg', 'svgz')
    .content_type in ('image/svg+xml')
    .file_type is 'svg'
  - any of:
    
    file.parse_text(., encodings=['ascii', 'utf8', 'utf16-le']).text matches any of 9 patterns
    
    *onload*
    *window.location.href*
    *onerror*
    *CDATA*
    *<script*
    *</script*
    *atob*
    *location.assign*
    *decodeURIComponent*
    file.parse_text(., encodings=['ascii', 'utf8', 'utf16-le']).text matches '<iframe[^\\>]+src\\s*=\\s*\\"data:[^\\;]+;base64,'
    any of beta.scan_base64(...) where:
    
    . matches any of 9 patterns
    
    *onload*
    *window.location.href*
    *onerror*
    *CDATA*
    *<script*
    *</script*
    *atob*
    *location.assign*
    *decodeURIComponent*
- all of:
  - any of:
    
    .file_extension in $file_extensions_common_archives
    .file_type is 'gz'
    .content_type is 'application/x-gzip'
  - any of file.explode(.) where all hold:
    
    any of:
    
    .file_extension in ('svg', 'svgz')
    .flavors.mime is 'image/svg+xml'
    any of .scan.strings.strings where:
    
    . matches any of 9 patterns
    
    *onload*
    *window.location.href*
    *onerror*
    *CDATA*
    *<script*
    *</script*
    *atob*
    *location.assign*
    *decodeURIComponent*

Inspects: attachments[].content_type, attachments[].file_extension, attachments[].file_type, type.inbound. Sensors: beta.scan_base64, file.explode, file.parse_text, regex.icontains, strings.ilike. Reference lists: $file_extensions_common_archives.

Indicators matched (19)

Field	Match	Value
`attachments[].file_extension`	member	`svg`
`attachments[].file_extension`	member	`svgz`
`attachments[].content_type`	member	`image/svg+xml`
`attachments[].file_type`	equals	`svg`
`strings.ilike`	substring	`onload`
`strings.ilike`	substring	`window.location.href`
`strings.ilike`	substring	`onerror`
`strings.ilike`	substring	`CDATA`
`strings.ilike`	substring	`<script`
`strings.ilike`	substring	`</script`
`strings.ilike`	substring	`atob`
`strings.ilike`	substring	`location.assign`

7 more

`strings.ilike`	substring	`decodeURIComponent`
`regex.icontains`	regex	`<iframe[^\>]+src\s=\s\"data:[^\;]+;base64,`
`attachments[].file_type`	equals	`gz`
`attachments[].content_type`	equals	`application/x-gzip`
`file.explode(attachments[])[].file_extension`	member	`svg`
`file.explode(attachments[])[].file_extension`	member	`svgz`
`file.explode(attachments[])[].flavors.mime`	equals	`image/svg+xml`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)