Code Review

ServiceNow Code Review

Overview

This skill covers systematic code review for ServiceNow scripts to identify and remediate:

• Security vulnerabilities (injection, XSS, privilege escalation, data exposure)
• Performance anti-patterns (unnecessary queries, N+1 problems, missing query limits)
• Platform best practice violations (API misuse, scope issues, deprecated methods)
• Maintainability concerns (naming, documentation, complexity, dead code)
• Concurrency and transaction safety issues
• Client-side performance and UX problems

When to use: Before deploying new scripts to production, during code review processes, when troubleshooting performance issues, or when auditing existing scripts for security compliance.

Prerequisites

• Roles: admin, security_admin, or developer with read access to script tables
• Access: sys_script, sys_script_include, sys_ui_script, sys_script_client tables
• Knowledge: ServiceNow scripting APIs, OWASP security principles, JavaScript best practices
• Related Skills: Complete development/code-assist for code generation context

Procedure

Step 1: Retrieve Scripts for Review

Query business rules for a specific table:

MCP Approach:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script
  query: collection=incident^active=true
  fields: sys_id,name,collection,when,script,filter_condition,order
  limit: 50

REST Alternative:

curl -u "$SN_USER:$SN_PASS" \
  "$SN_INSTANCE/api/now/table/sys_script?sysparm_query=collection=incident^active=true&sysparm_fields=sys_id,name,collection,when,script,filter_condition,order&sysparm_limit=50" \
  -H "Accept: application/json"

Query script includes:

MCP Approach:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script_include
  query: active=true^sys_updated_on>=javascript:gs.daysAgo(30)
  fields: sys_id,name,script,client_callable,access,api_name
  limit: 50

Query client scripts:

MCP Approach:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script_client
  query: table=incident^active=true
  fields: sys_id,name,table,type,fieldname,script,ui_type
  limit: 50

Step 2: Security Review Checklist

Review each script against these critical security patterns:

2a. SQL/GlideRecord Injection:

VULNERABILITY: Unsanitized user input in queries
BAD:
  gr.addEncodedQuery(current.variables.user_input);
  gr.addQuery('name', request.getParameter('name'));

GOOD:
  // Validate and sanitize input
  var sanitized = GlideStringUtil.escapeHTML(input);
  // Use parameterized queries
  gr.addQuery('name', sanitizedName);
  // Validate against allowlist
  var validFields = ['name', 'number', 'state'];
  if (validFields.indexOf(fieldName) === -1) return;

2b. Cross-Site Scripting (XSS):

VULNERABILITY: Unescaped output in UI scripts or HTML fields
BAD:
  element.innerHTML = current.short_description;
  gs.getMessage(userInput);

GOOD:
  element.textContent = current.short_description;
  var escaped = GlideStringUtil.escapeHTML(current.short_description);

2c. Privilege Escalation:

VULNERABILITY: Missing role checks or using setWorkflow(false) inappropriately
BAD:
  current.setWorkflow(false); // Bypasses business rules and ACLs
  current.autoSysFields(false); // Hides audit trail

GOOD:
  // Only bypass when absolutely necessary and documented
  if (gs.hasRole('admin')) {
    current.setWorkflow(false); // REASON: Bulk import requires bypass
  }

2d. Sensitive Data Exposure:

VULNERABILITY: Logging or returning sensitive data
BAD:
  gs.log('User password: ' + password);
  gs.log('SSN: ' + current.social_security_number);

GOOD:
  gs.log('Authentication attempted for user: ' + username);
  // Never log PII, credentials, or tokens

Step 3: Performance Review Checklist

3a. Unbounded GlideRecord Queries:

ANTI-PATTERN: Query without limit
BAD:
  var gr = new GlideRecord('incident');
  gr.addQuery('active', true);
  gr.query(); // Could return millions of records

GOOD:
  var gr = new GlideRecord('incident');
  gr.addQuery('active', true);
  gr.setLimit(1000); // Always set a reasonable limit
  gr.query();

3b. N+1 Query Pattern:

ANTI-PATTERN: Query inside a loop
BAD:
  var incidents = new GlideRecord('incident');
  incidents.query();
  while (incidents.next()) {
    var user = new GlideRecord('sys_user');
    user.get(incidents.caller_id); // Query per iteration!
    // process...
  }

GOOD:
  // Use dot-walking or join queries
  var incidents = new GlideRecord('incident');
  incidents.addQuery('active', true);
  incidents.query();
  while (incidents.next()) {
    var callerName = incidents.caller_id.getDisplayValue(); // Dot-walk
    // process...
  }

  // Or use GlideAggregate for counts
  var ga = new GlideAggregate('incident');
  ga.addQuery('active', true);
  ga.groupBy('assignment_group');
  ga.addAggregate('COUNT');
  ga.query();

3c. Synchronous GlideRecord in Client Scripts:

ANTI-PATTERN: Synchronous server calls from client
BAD:
  var gr = new GlideRecord('sys_user');
  gr.addQuery('sys_id', userId);
  gr.query(); // Synchronous - blocks browser!
  if (gr.next()) { ... }

GOOD:
  // Use GlideAjax for async server calls
  var ga = new GlideAjax('MyScriptInclude');
  ga.addParam('sysparm_name', 'getUserInfo');
  ga.addParam('sysparm_user_id', userId);
  ga.getXMLAnswer(function(answer) {
    // Process response asynchronously
  });

3d. Unnecessary Field Retrieval:

ANTI-PATTERN: Selecting all fields when only a few are needed
BAD:
  var gr = new GlideRecord('incident');
  gr.query(); // Returns ALL fields

GOOD:
  var gr = new GlideRecord('incident');
  gr.addQuery('active', true);
  gr.chooseWindow(0, 100);
  gr.setFields('sys_id,number,short_description,state');
  gr.query();

Step 4: Platform Best Practices Review

4a. Deprecated API Usage:

DEPRECATED: Avoid these methods
BAD:
  current.getDisplayValue(); // Without field name - ambiguous
  gs.log(); // Use gs.info/warn/error instead
  Packages.java.lang.*; // Direct Java calls - unsupported

GOOD:
  current.getDisplayValue('short_description');
  gs.info('Message: {0}', current.number);

4b. Scope Violations:

ANTI-PATTERN: Accessing global scope from scoped app
BAD:
  // In scoped app, directly calling global
  var result = new IncidentUtils(); // Global script include

GOOD:
  // Use scoped API or cross-scope access
  var si = new global.IncidentUtils(); // Explicit scope prefix
  // Or use sn_ws for REST-based cross-scope communication

4c. Business Rule Ordering:

BEST PRACTICE: Proper ordering
- 100: Data defaults and initialization
- 200: Validation rules
- 300: Data transformation
- 400: Cross-table updates (after rules)
- 500+: Notifications and integrations (after rules)

4d. GlideRecord getValue vs Direct Access:

ANTI-PATTERN: Direct field access for comparisons
BAD:
  if (current.state == 6) { ... } // Returns GlideElement, not value

GOOD:
  if (current.getValue('state') == '6') { ... }
  // Or use typed comparison
  if (current.state.changesTo(6)) { ... }

Step 5: Client Script Review

5a. DOM Manipulation:

ANTI-PATTERN: Direct DOM manipulation
BAD:
  document.getElementById('incident.short_description').style.color = 'red';
  $('incident.state').value = '6';

GOOD:
  g_form.setMandatory('short_description', true);
  g_form.addDecoration('short_description', 'color_red');
  g_form.setValue('state', '6');

5b. Missing isLoading Check:

ANTI-PATTERN: onChange without isLoading guard
BAD:
  function onChange(control, oldValue, newValue, isLoading) {
    // Fires on every form load, causing unnecessary processing
    callServer(newValue);
  }

GOOD:
  function onChange(control, oldValue, newValue, isLoading) {
    if (isLoading || newValue === '') {
      return;
    }
    callServer(newValue);
  }

Step 6: Generate Review Report

Compile findings into a structured review report:

Code Review Report
================================================
Script: [Script Name]
Table: [Table Name]
Type: [Business Rule / Client Script / Script Include]
Reviewer: [AI-Assisted Review]
Date: [Current Date]

CRITICAL ISSUES:
  [C1] Security - SQL Injection in line X
  [C2] Security - XSS vulnerability in line Y

HIGH ISSUES:
  [H1] Performance - N+1 query pattern in line Z
  [H2] Performance - Unbounded GlideRecord query

MEDIUM ISSUES:
  [M1] Best Practice - Deprecated API usage
  [M2] Best Practice - Missing error handling

LOW ISSUES:
  [L1] Maintainability - Missing JSDoc comments
  [L2] Maintainability - Variable naming inconsistency

RECOMMENDATIONS:
  1. [Specific fix for C1]
  2. [Specific fix for C2]
  3. [Specific fix for H1]

Step 7: Apply Fixes

Update script with fixes:

MCP Approach:

Tool: SN-Update-Record
Parameters:
  table_name: sys_script
  sys_id: [script_sys_id]
  data:
    script: |
      // [Updated script with fixes applied]

REST Alternative:

curl -u "$SN_USER:$SN_PASS" \
  "$SN_INSTANCE/api/now/table/sys_script/[script_sys_id]" \
  -H "Content-Type: application/json" \
  -X PATCH \
  -d '{"script": "// Updated script content"}'

Tool Usage

Best Practices

• Review in layers: Security first, then performance, then best practices, then maintainability
• Automate recurring checks: Build scanning scripts for common anti-patterns
• Check all script types together: Business rules, client scripts, and script includes often interact
• Test fixes in sub-production: Never apply code fixes directly to production
• Document exceptions: If a known anti-pattern is intentional, add a comment explaining why
• Review ACLs alongside scripts: Ensure ACLs complement business rule security checks
• Check for dead code: Inactive scripts still count against instance performance during upgrades
• Validate error handling: Every GlideRecord.get() should check for null results
• Review update sets: Check that scripts are captured in proper update sets before promoting

Troubleshooting

Cannot Access Script Tables

Symptom: Permission denied when querying sys_script Cause: Missing admin or script-related roles Solution: Verify role assignment:

Tool: SN-Query-Table
Parameters:
  table_name: sys_user_has_role
  query: user=[user_sys_id]^role.name=admin
  fields: sys_id,role,user

Script Too Large to Retrieve

Symptom: Script field truncated in API response Cause: API field size limits Solution: Get the specific record directly:

Tool: SN-Get-Record
Parameters:
  table_name: sys_script
  sys_id: [script_sys_id]
  fields: script

Finding All Scripts Modified Recently

Symptom: Need to review all recent changes Solution:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script
  query: sys_updated_on>=javascript:gs.daysAgo(7)^active=true
  fields: sys_id,name,collection,when,sys_updated_by,sys_updated_on
  limit: 100

Identifying Duplicate or Conflicting Rules

Symptom: Unexpected behavior from multiple rules on same table Solution:

Tool: SN-Query-Table
Parameters:
  table_name: sys_script
  query: collection=incident^active=true^when=before
  fields: sys_id,name,order,filter_condition,action_insert,action_update
  limit: 100

Examples

Example 1: Full Security Audit of Incident Business Rules

# Step 1: Get all active business rules for incident table
Tool: SN-Query-Table
Parameters:
  table_name: sys_script
  query: collection=incident^active=true
  fields: sys_id,name,when,script,order
  limit: 100

# Step 2: For each script, check for security patterns
# Look for: addEncodedQuery with user input, setWorkflow(false),
# gs.log with sensitive data, eval() usage, Packages.* calls

# Step 3: Get client scripts for incident
Tool: SN-Query-Table
Parameters:
  table_name: sys_script_client
  query: table=incident^active=true
  fields: sys_id,name,type,script
  limit: 50

# Step 4: Check for synchronous GlideRecord in client scripts
# Look for: GlideRecord().query() without callback, direct DOM access

Example 2: Performance Review of Script Includes

# Get all active script includes with recent updates
Tool: SN-Query-Table
Parameters:
  table_name: sys_script_include
  query: active=true^sys_updated_on>=javascript:gs.daysAgo(90)
  fields: sys_id,name,script,api_name
  limit: 100

# For each script include, check for:
# - GlideRecord queries without setLimit()
# - Nested loops with queries (N+1)
# - Missing null checks after .get()
# - Large string concatenation in loops

Example 3: Review Recently Deployed Code

# Get scripts from the latest update set
Tool: SN-Query-Table
Parameters:
  table_name: sys_update_xml
  query: update_set=[update_set_sys_id]^nameLIKEsys_script
  fields: sys_id,name,action,target_name
  limit: 50

# Then retrieve each script for review
Tool: SN-Get-Record
Parameters:
  table_name: sys_script
  sys_id: [script_sys_id]
  fields: name,script,collection,when

Related Skills

• development/code-assist - AI-assisted code generation
• security/acl-management - Access control list management
• admin/update-set-management - Update set handling for deployments
• security/audit-compliance - Security hardening guidelines