A tiny bit more detail from ABC:
The GOP minority does not have subpoena power, much to their chagrin, although Republicans changed the playbook in 2015 when they rewrote rules delegating subpoena power to individual chairmen without full approval from the House of Representatives.
Democrats reaffirmed that process earlier this year, adopting impeachment rules that includ[e] granting their chairmen the right to issue subpoenas unilaterally.
So I think that's the change that CNN is referring to. I haven't yet found the exact text of the decision, but we know its substance and year now.
And the exact rule in which this change is incorporated is
Rule XI, clause 2(m)(3) also allows committees to adopt rules to delegate the authorization and
issuance of subpoenas to a committee’s chair “under such rules and under such limitations as the
committee may prescribe.” This same subparagraph requires subpoenas to be signed by the chair
or by a member who has been designated by the committee.
And the full text from Jefferson's Manual, 2017 edition (pp. 582-584):
Power to sit and act; subpoena power
(m)(1) For the purpose of carrying out any of
its functions and duties under this
rule and rule X (including any matters
referred to it under clause 2 of rule XII), a committee or subcommittee is authorized
(subject to subparagraph (3)(A))—
(A) to sit and act at such times and places
within the United States, whether the House
is in session, has recessed, or has adjourned,
and to hold such hearings as it considers necessary;
(B) to require, by subpoena or otherwise, the
attendance and testimony of such witnesses
and the production of such books, records, correspondence,
memoranda, papers, and documents
as it considers necessary.
(2) The chair of the committee, or a member
designated by the chair, may administer oaths
(3)(A)(i) Except as provided in subdivision
(A)(ii), a subpoena may be authorized and issued
by a committee or subcommittee under subparagraph
(1)(B) in the conduct of an investigation or
series of investigations or activities only when
authorized by the committee or subcommittee, a
majority being present. The power to authorize
and issue subpoenas under subparagraph (1)(B)
may be delegated to the chair of the committee
under such rules and under such limitations as
the committee may prescribe. Authorized subpoenas
shall be signed by the chair of the committee
or by a member designated by the committee.
(ii) In the case of a subcommittee of the Committee
on Ethics, a subpoena may be authorized
and issued only by an affirmative vote of a majority
of its members.
(B) A subpoena duces tecum may specify
terms of return other than at a meeting or hearing
of the committee or subcommittee authorizing
(C) Compliance with a subpoena issued by a
committee or subcommittee under subparagraph
(1)(B) may be enforced only as authorized or directed
by the House.
And the history of changes of that XI (m)(3) is also given in Jefferson's Manual, but I'm quoting only a part of it:
Before the adoption of clause 2(m) under the Committee Reform Amendments
of 1974, effective January 3, 1975 (H. Res. 988, 93d Cong., Oct.
8, 1974, p. 34470), only the Committees on Appropriations, the Budget,
Government Operations, Internal Security, and Standards of Official Conduct
were permitted by the standing rules to perform the functions as
specified in subparagraphs (1)(A) and (1)(B), and other standing and select
committees were given those authorities by separate resolutions reported
from the Committee on Rules each Congress. In the 94th Congress the
paragraph was amended to require authorized subpoenas to be signed by
the chair of the full committee or any member designated by the committee
(H. Res. 5, Jan. 14, 1975, p. 20). In the 95th Congress the paragraph was
amended to permit a subcommittee, as well as a full committee, to authorize
subpoenas and to allow a full committee to delegate such authority
to the chair of the full committee (H. Res. 5, Jan. 4, 1977, pp. 53–70).
The special rule for authorizing and issuing a subpoena of a subcommittee
of the Committee on Ethics (formerly Standards of Official Conduct) was
adopted in the 105th Congress (sec. 15, H. Res. 168, Sept. 18, 1997, p.
19319). In the 106th Congress subparagraph (3)(B) was added, and clerical
and stylistic changes were effected when the House recodified its rules
in the same Congress (H. Res. 5, Jan. 6, 1999, p. 47). A clerical correction
was effected to paragraph (m)(1) in the 107th Congress to correct a cross
reference (sec. 2(x), H. Res. 5, Jan. 3, 2001, p. 26). Gender-based references
were eliminated in the 111th Congress (sec. 2(l), H. Res. 5, Jan. 6, 2009,
p. 7). This paragraph was amended in the 112th Congress to reflect a
change in committee name (sec. 2(e)(8), H. Res. 5, Jan. 5, 2011, p. 80).
A subpoena issued under this clause need only be signed by the chair
of the committee or by any member designated by the committee, whereas
when the House issues an order or warrant the Speaker must under clause
4 of rule I issue the summons under the Speaker’s hand and seal, and
it must be attested by the Clerk pursuant to clause 2(d) of rule II (formerly
clause 3 of rule III) (III, 1668; see H. Rept. 96–1078, p. 22). A statute
empowers the chair of the Committee of the Whole, the Speaker, chairs
of joint, select, or standing committees, and Members to administer oaths
to witnesses (2 U.S.C. 191; III, 1769).
There's another (pretty long) paragraph on the history of clause (ii) that governs subpoenas issued by the Committee on Ethics, but since that's not involved in the impeachment (as far as I can tell, that committee apparently deals with malfeasances of Congress members) I'm not quoting it here.
So the rules which allow the committees (except Ethics) to make their own rules for subpoenas are actually not that new. It's not clear to me where the committee-specific rules are recorded. It is possible that ABC is correct and whatever committees were involved in the Obama inquiries changed their committee-specific rules to take full advantage of XI (m)(3) in 2015, but I'm not sure how to check that in official records.
There is however a 2015 Politico article on that:
Democratic lawmakers are harshly criticizing House Republicans for altering committee rules governing how chairmen can subpoena witnesses and documents.
In a letter shared with POLITICO, the Democrats slams the GOP conference for changing rules on a number of House committees to make it easier for Republicans to subpoena witnesses without consultation or approval from minority lawmakers - an effort that came as Republicans are preparing aggressive oversight efforts for President Barack Obama’s final two years in office.
Sixteen Democrats, all ranking members of House committees, accused Republicans of attempting to create Darrell Issa-like committee structures, referring to the former Oversight and Government Reform chairman who was criticized by Democrats for his dogged probes into the White House.
“For decades, responsible committee chairmen—both Democratic and Republican—recognized that the coercive power of subpoenas should be used only as a last resort, and they obtained the concurrence of the ranking member or called a committee vote before issuing subpoenas,” the lawmakers wrote on Tuesday.
In January, Republicans moved to give a number of key committees, including the Energy and Commerce Committee, the Judiciary Committee and the Financial Services Committee new subpoena powers. A handful of other committees also considered changing their governing rules.
For a number of panels, rule change would eliminate long-standing requirements that the chairmen either consult or get consent from the minority party before issuing subpoenas for testimony and documents or hold a majority vote. The committees who saw rule changes include panels with oversight into controversial Obama policies like the Dodd-Frank financial regulations law, immigration and Obamacare.
“This year House Republicans are changing the rules to give some chairmen unfettered authority to issue subpoenas unilaterally, adopting an abusive model embraced only by Senator Joe McCarthy, former Rep. Dan Burton, and Rep. Darrell Issa,” the lawmakers wrote. “To their credit, some well-functioning committees, such as the Committees on Appropriations, Armed Services, Intelligence, and Veterans Affairs, did not expand subpoena power for their chairmen.”
At the time, Republican defended the rule change as necessary to effectively investigate the Obama administration.
So yeah, those 2015 changes were committee-specific rule changes apparently made by the committees themselves, changes which were permissible under the standing House rules. Interestingly, that article says that the Intelligence committee did not change its rules at the time. I'm guessing they've done that after 2015.
A subsequent 2018 article in Politico notes:
Democrats eager to investigate the Trump administration if they seize the House would have the GOP to thank for one of their most potent tools — a sweeping subpoena authority that Democratic lawmakers denounced as an abusive power grab three years ago.
House Republicans changed the rules in 2015 to allow many of their committee chairmen to issue subpoenas without consulting the minority party, overriding Democrats objections that likened the tactic to something out of the McCarthy era.
Now the weapon that the GOP wielded dozens of times against President Barack Obama’s agencies could allow Democrats to bombard President Donald Trump’s most controversial appointees with demands for information. And many Democrats are itching to use it.
“The Republicans have set the standard and, by God, we’re going to emulate that standard,” Rep. Gerry Connolly (D-Va.) told POLITICO.
Before the 2015 rule change, most House subpoenas needed at least some bipartisan cover, requiring a majority vote of committee members and consultation with a panel’s ranking member. The change erased those requirements and allowed the chairmen to proceed unilaterally, although the exact rules vary by committee.
Of the 21 standing committees in the House, 14 allow their chairmen to issue subpoenas on their own initiative, according to the Congressional Research Service.
And in that 2018 CRS document, the Intelligence committee (last row) is also listed as capable of sending subpoenas on the chair's initiative, but it also has a check for the ranking minority member being consulted. Notably however, no committee has a requirement (anymore) for the ranking minority member to concur.