diff --git a/erpnext/accounts/doctype/financial_report_template/financial_report_engine.py b/erpnext/accounts/doctype/financial_report_template/financial_report_engine.py
index 1137b79a964..e182a0db48e 100644
--- a/erpnext/accounts/doctype/financial_report_template/financial_report_engine.py
+++ b/erpnext/accounts/doctype/financial_report_template/financial_report_engine.py
@@ -479,7 +479,10 @@ class DataCollector:
 		if company:
 			query = query.where(account.company == company)
 
-		if conditions := filter_parser.build_conditions(account_rows, account):
+		# filters are optional: no filter means all (enabled, non-group) accounts of the company.
+		# invalid filters can't reach here — build_conditions raises on them (raise_on_invalid).
+		conditions = filter_parser.build_conditions(account_rows, account, raise_on_invalid=True)
+		if conditions is not None:
 			query = query.where(conditions)
 
 		return query.run(pluck=True)
@@ -791,17 +794,20 @@ class FilterExpressionParser:
 	def __init__(self):
 		self.validator = AccountFilterValidator()
 
-	def build_conditions(self, report_rows, table):
+	def build_conditions(self, report_rows, table, raise_on_invalid=False):
 		conditions = []
 		for row in report_rows or []:
-			condition = self.build_condition(row, table)
+			condition = self.build_condition(row, table, raise_on_invalid=raise_on_invalid)
 			if condition is not None:
 				conditions.append(condition)
 
+		if not conditions:
+			return None
+
 		# ensure brackets in or condition
 		return reduce(lambda a, b: (a) | (b), conditions)
 
-	def build_condition(self, report_row, table):
+	def build_condition(self, report_row, table, raise_on_invalid=False):
 		"""
 		Build SQL condition directly from filter formula.
 
@@ -831,9 +837,11 @@ class FilterExpressionParser:
 		if not filter_formula:
 			return None
 
-		errors = self.validator.validate(report_row)
+		errors = self.validator.validate_filter(report_row)
 		if not errors.is_valid:
 			error_messages = [str(issue) for issue in errors.issues]
+			if raise_on_invalid:
+				frappe.throw("<br><br>".join(error_messages), title=_("Invalid Filter"))
 			frappe.log_error(f"Filter validation errors found:\n{'<br><br>'.join(error_messages)}")
 			return None
 
@@ -1023,7 +1031,11 @@ class FormulaFieldUpdater:
 
 @frappe.whitelist()
 def get_filtered_accounts(company: str, account_rows: str | list):
+	if not company:
+		frappe.throw(_("Company is required"), title=_("Missing Company"))
+
 	frappe.has_permission("Financial Report Template", ptype="read", throw=True)
+	frappe.has_permission("Company", doc=company, throw=True)
 
 	if isinstance(account_rows, str):
 		account_rows = json.loads(account_rows, object_hook=frappe._dict)
diff --git a/erpnext/accounts/doctype/financial_report_template/financial_report_validation.py b/erpnext/accounts/doctype/financial_report_template/financial_report_validation.py
index 5f187006c7b..4ecdd126eb3 100644
--- a/erpnext/accounts/doctype/financial_report_template/financial_report_validation.py
+++ b/erpnext/accounts/doctype/financial_report_template/financial_report_validation.py
@@ -403,10 +403,19 @@ class AccountFilterValidator(Validator):
 		self.account_fields = account_fields or set(self.account_meta._valid_columns)
 
 	def validate(self, row) -> ValidationResult:
-		result = ValidationResult()
-
+		# dispatch-path guard: only account-data rows are validated here
 		if row.data_source != "Account Data":
-			return result
+			return ValidationResult()
+
+		return self.validate_filter(row)
+
+	def validate_filter(self, row) -> ValidationResult:
+		"""Validate calculation_formula as an Account filter, regardless of data_source.
+
+		The caller has already decided this row is an account filter, so unlike
+		`validate()` this does not opt out based on `data_source`.
+		"""
+		result = ValidationResult()
 
 		try:
 			filter_config = json.loads(row.calculation_formula)
@@ -420,7 +429,7 @@ class AccountFilterValidator(Validator):
 				result.add_error(
 					ValidationIssue(
 						message=_("[{0}] {1}", context="Financial Report Template").format(
-							get_formula_field_label(row.data_source), error
+							get_formula_field_label("Account Data"), error
 						),
 						row_idx=row.idx,
 					)
@@ -430,7 +439,7 @@ class AccountFilterValidator(Validator):
 			result.add_error(
 				ValidationIssue(
 					message=_("[{0}] {1}", context="Financial Report Template").format(
-						get_formula_field_label(row.data_source),
+						get_formula_field_label("Account Data"),
 						_("Invalid JSON format: {0}").format(str(e)),
 					),
 					row_idx=row.idx,
@@ -455,10 +464,9 @@ class AccountFilterValidator(Validator):
 			if not isinstance(field, str) or not isinstance(operator, str):
 				return _("Field and operator must be strings")
 
-			display = (field if advanced_filtering else self.account_meta.get_label(field)) or field
-
 			if field not in account_fields:
-				return _("Field '{0}' is not a valid Account field").format(display)
+				# escape: `field` is caller-supplied and this message renders as HTML
+				return _("Field '{0}' is not a valid Account field").format(frappe.utils.escape_html(field))
 
 			if operator.casefold() not in OPERATOR_MAP:
 				return _("Invalid operator '{0}'").format(operator)
diff --git a/erpnext/accounts/doctype/financial_report_template/test_financial_report_template.py b/erpnext/accounts/doctype/financial_report_template/test_financial_report_template.py
index e49cc4c8333..7b23398a472 100644
--- a/erpnext/accounts/doctype/financial_report_template/test_financial_report_template.py
+++ b/erpnext/accounts/doctype/financial_report_template/test_financial_report_template.py
@@ -5,6 +5,7 @@ import frappe
 from frappe.tests.utils import whitelist_for_tests
 
 from erpnext.accounts.doctype.financial_report_template.financial_report_validation import (
+	AccountFilterValidator,
 	FormulaValidator,
 	get_valid_api_method,
 )
@@ -164,3 +165,86 @@ class TestCustomAPIValidation(FinancialReportTemplateTestCase):
 			result = validator.validate(row)
 			self.assertFalse(result.is_valid)
 			self.assertEqual(len(frappe.local.message_log), message_count)
+
+
+class TestAccountFilter(FinancialReportTemplateTestCase):
+	"""Filter fields must be validated on the account-filter parser path."""
+
+	@staticmethod
+	def _row(formula, **extra):
+		return frappe._dict(calculation_formula=formula, idx=1, **extra)
+
+	def test_validate_filter_enforces_allow_list_without_data_source(self):
+		# the parser path has no `data_source`; the field allow-list must still apply
+		validator = AccountFilterValidator()
+		self.assertFalse(validator.validate_filter(self._row('["bad_field", "=", "x"]')).is_valid)
+		self.assertTrue(validator.validate_filter(self._row('["root_type", "=", "Income"]')).is_valid)
+
+	def test_validate_gate_still_opts_out_for_non_account_data(self):
+		# validate() is the dispatch gate: it must not validate non "Account Data" rows
+		validator = AccountFilterValidator()
+		row = self._row('["bad_field", "=", "x"]', data_source="Custom API")
+		self.assertTrue(validator.validate(row).is_valid)
+
+	def test_error_message_labels_and_escapes_field(self):
+		validator = AccountFilterValidator()
+		result = validator.validate_filter(self._row('["<script>", "=", "x"]'))
+		message = str(result.issues[0])
+		self.assertIn("[Account Filter]", message)
+		self.assertIn("&lt;script&gt;", message)
+		self.assertNotIn("<script>", message)
+
+	def test_build_conditions_raises_on_invalid_field_when_opted_in(self):
+		from erpnext.accounts.doctype.financial_report_template.financial_report_engine import (
+			FilterExpressionParser,
+		)
+
+		account = frappe.qb.DocType("Account")
+		rows = [self._row('["bad_field", "=", "x"]')]
+		parser = FilterExpressionParser()
+
+		# default: invalid rows are skipped, not raised
+		self.assertIsNone(parser.build_conditions(rows, account))
+
+		# opted in (the get_filtered_accounts path): invalid rows raise
+		self.assertRaises(
+			frappe.ValidationError, parser.build_conditions, rows, account, raise_on_invalid=True
+		)
+
+	def test_build_conditions_empty_returns_none(self):
+		from erpnext.accounts.doctype.financial_report_template.financial_report_engine import (
+			FilterExpressionParser,
+		)
+
+		account = frappe.qb.DocType("Account")
+		self.assertIsNone(FilterExpressionParser().build_conditions([], account))
+
+	def test_endpoint_requires_company(self):
+		from erpnext.accounts.doctype.financial_report_template.financial_report_engine import (
+			get_filtered_accounts,
+		)
+
+		self.assertRaises(frappe.ValidationError, get_filtered_accounts, "", "[]")
+
+	def test_endpoint_rejects_invalid_field(self):
+		from erpnext.accounts.doctype.financial_report_template.financial_report_engine import (
+			get_filtered_accounts,
+		)
+
+		company = frappe.get_all("Company", limit=1, pluck="name")[0]
+		rows = frappe.as_json([{"calculation_formula": '["bad_field", "=", "x"]'}])
+		self.assertRaises(frappe.ValidationError, get_filtered_accounts, company, rows)
+
+	def test_endpoint_empty_rows_returns_all_company_accounts(self):
+		# filters are optional: no filter returns every enabled, non-group account of the company
+		from erpnext.accounts.doctype.financial_report_template.financial_report_engine import (
+			get_filtered_accounts,
+		)
+
+		company = frappe.get_all("Company", limit=1, pluck="name")[0]
+		expected = frappe.get_all(
+			"Account",
+			filters={"company": company, "disabled": 0, "is_group": 0},
+			pluck="name",
+		)
+		self.assertEqual(sorted(get_filtered_accounts(company, "[]")), sorted(expected))