Cloudflare - XSS probing pattern in request

let s_threshold = 3;
Cloudflare
| where HttpRequestMethod in~ ('POST', 'PUT')
| extend susp_ch = countof(ClientRequestURI, '%00')
| where ClientRequestURI matches regex @'(alert\()|(alert\%28)|(String\.fromCharCode\()|(expression\(alert)' or susp_ch > s_threshold
| extend IPCustomEntity = SrcIpAddr
| extend UrlCustomEntity = ClientRequestURI

relevantTechniques:
- T1190
- T1133
name: Cloudflare - XSS probing pattern in request
requiredDataConnectors:
- dataTypes:
  - Cloudflare
  connectorId: CloudflareDataConnector
entityMappings:
- fieldMappings:
  - identifier: Address
    columnName: IPCustomEntity
  entityType: IP
- fieldMappings:
  - identifier: Url
    columnName: UrlCustomEntity
  entityType: URL
triggerThreshold: 0
id: 4d9d00b9-31a6-49e4-88c1-9e68277053ac
tactics:
- InitialAccess
version: 1.0.0
OriginalUri: https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Cloudflare/Analytic Rules/CloudflareXSSProbingPattern.yaml
queryPeriod: 1h
kind: Scheduled
queryFrequency: 1h
severity: Medium
status: Available
description: |
    'Detects XSS probing patterns.'
query: |
  let s_threshold = 3;
  Cloudflare
  | where HttpRequestMethod in~ ('POST', 'PUT')
  | extend susp_ch = countof(ClientRequestURI, '%00')
  | where ClientRequestURI matches regex @'(alert\()|(alert\%28)|(String\.fromCharCode\()|(expression\(alert)' or susp_ch > s_threshold
  | extend IPCustomEntity = SrcIpAddr
  | extend UrlCustomEntity = ClientRequestURI  
triggerOperator: gt

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "parameters": {
    "workspace": {
      "type": "String"
    }
  },
  "resources": [
    {
      "apiVersion": "2024-01-01-preview",
      "id": "[concat(resourceId('Microsoft.OperationalInsights/workspaces/providers', parameters('workspace'), 'Microsoft.SecurityInsights'),'/alertRules/4d9d00b9-31a6-49e4-88c1-9e68277053ac')]",
      "kind": "Scheduled",
      "name": "[concat(parameters('workspace'),'/Microsoft.SecurityInsights/4d9d00b9-31a6-49e4-88c1-9e68277053ac')]",
      "properties": {
        "alertRuleTemplateName": "4d9d00b9-31a6-49e4-88c1-9e68277053ac",
        "customDetails": null,
        "description": "'Detects XSS probing patterns.'\n",
        "displayName": "Cloudflare - XSS probing pattern in request",
        "enabled": true,
        "entityMappings": [
          {
            "entityType": "IP",
            "fieldMappings": [
              {
                "columnName": "IPCustomEntity",
                "identifier": "Address"
              }
            ]
          },
          {
            "entityType": "URL",
            "fieldMappings": [
              {
                "columnName": "UrlCustomEntity",
                "identifier": "Url"
              }
            ]
          }
        ],
        "OriginalUri": "https://github.com/Azure/Azure-Sentinel/blob/master/Solutions/Cloudflare/Analytic Rules/CloudflareXSSProbingPattern.yaml",
        "query": "let s_threshold = 3;\nCloudflare\n| where HttpRequestMethod in~ ('POST', 'PUT')\n| extend susp_ch = countof(ClientRequestURI, '%00')\n| where ClientRequestURI matches regex @'(alert\\()|(alert\\%28)|(String\\.fromCharCode\\()|(expression\\(alert)' or susp_ch > s_threshold\n| extend IPCustomEntity = SrcIpAddr\n| extend UrlCustomEntity = ClientRequestURI\n",
        "queryFrequency": "PT1H",
        "queryPeriod": "PT1H",
        "severity": "Medium",
        "status": "Available",
        "subTechniques": [],
        "suppressionDuration": "PT1H",
        "suppressionEnabled": false,
        "tactics": [
          "InitialAccess"
        ],
        "techniques": [
          "T1133",
          "T1190"
        ],
        "templateVersion": "1.0.0",
        "triggerOperator": "GreaterThan",
        "triggerThreshold": 0
      },
      "type": "Microsoft.OperationalInsights/workspaces/providers/alertRules"
    }
  ]
}